ARM: fix asm/memory.h build error

Jason Gunthorpe reports a build failure when ARM_PATCH_PHYS_VIRT is
not defined:

In file included from arch/arm/include/asm/page.h:163:0,
                 from include/linux/mm_types.h:16,
                 from include/linux/sched.h:24,
                 from arch/arm/kernel/asm-offsets.c:13:
arch/arm/include/asm/memory.h: In function '__virt_to_phys':
arch/arm/include/asm/memory.h:244:40: error: 'PHYS_OFFSET' undeclared (first use in this function)
arch/arm/include/asm/memory.h:244:40: note: each undeclared identifier is reported only once for each function it appears in
arch/arm/include/asm/memory.h: In function '__phys_to_virt':
arch/arm/include/asm/memory.h:249:13: error: 'PHYS_OFFSET' undeclared (first use in this function)

Fixes: ca5a45c06cd4 ("ARM: mm: use phys_addr_t appropriately in p2v and v2p conversions")
Tested-By: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index 9ecccc8..6976b03 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -100,23 +100,19 @@
 #define TASK_UNMAPPED_BASE	UL(0x00000000)
 #endif
 
-#ifndef PHYS_OFFSET
-#define PHYS_OFFSET 		UL(CONFIG_DRAM_BASE)
-#endif
-
 #ifndef END_MEM
 #define END_MEM     		(UL(CONFIG_DRAM_BASE) + CONFIG_DRAM_SIZE)
 #endif
 
 #ifndef PAGE_OFFSET
-#define PAGE_OFFSET		(PHYS_OFFSET)
+#define PAGE_OFFSET		PLAT_PHYS_OFFSET
 #endif
 
 /*
  * The module can be at any place in ram in nommu mode.
  */
 #define MODULES_END		(END_MEM)
-#define MODULES_VADDR		(PHYS_OFFSET)
+#define MODULES_VADDR		PAGE_OFFSET
 
 #define XIP_VIRT_ADDR(physaddr)  (physaddr)
 
@@ -157,6 +153,16 @@
 #endif
 #define ARCH_PGD_MASK		((1 << ARCH_PGD_SHIFT) - 1)
 
+/*
+ * PLAT_PHYS_OFFSET is the offset (from zero) of the start of physical
+ * memory.  This is used for XIP and NoMMU kernels, or by kernels which
+ * have their own mach/memory.h.  Assembly code must always use
+ * PLAT_PHYS_OFFSET and not PHYS_OFFSET.
+ */
+#ifndef PLAT_PHYS_OFFSET
+#define PLAT_PHYS_OFFSET	UL(CONFIG_PHYS_OFFSET)
+#endif
+
 #ifndef __ASSEMBLY__
 
 /*
@@ -239,6 +245,8 @@
 
 #else
 
+#define PHYS_OFFSET	PLAT_PHYS_OFFSET
+
 static inline phys_addr_t __virt_to_phys(unsigned long x)
 {
 	return (phys_addr_t)x - PAGE_OFFSET + PHYS_OFFSET;
@@ -251,17 +259,6 @@
 
 #endif
 #endif
-#endif /* __ASSEMBLY__ */
-
-#ifndef PHYS_OFFSET
-#ifdef PLAT_PHYS_OFFSET
-#define PHYS_OFFSET	PLAT_PHYS_OFFSET
-#else
-#define PHYS_OFFSET	UL(CONFIG_PHYS_OFFSET)
-#endif
-#endif
-
-#ifndef __ASSEMBLY__
 
 /*
  * PFNs are used to describe any physical page; this means