ARM: make the physical-relative calculation more obvious

The physical-relative calculation between the XIP text and data sections
introduced by the previous patch was far from obvious. Let's simplify it
by turning it into a macro which takes the two (virtual) addresses.

This allows us to arrange the calculation in a more obvious manner - we
can make it two sub-expressions which calculate the physical address for
each symbol, and then takes the difference of those physical addresses.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 1595fb2..0f8963a 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -487,7 +487,7 @@
 
 	.align	2
 __v7_setup_stack_ptr:
-	.word	__v7_setup_stack - . + PHYS_OFFSET_FIXUP
+	.word	PHYS_RELATIVE(__v7_setup_stack, .)
 ENDPROC(__v7_setup)
 
 	.bss