[XTENSA] clean-up header files

The header files in the asm-xtensa directory are not clean and
'make headers_check' fails. This is a first patch to fix most of
the header files. It removes unnecessary include statements and
adds some that are required for building the kernel. The linker
script required some updates or the linking stage would fail.

Signed-off-by: Chris Zankel <chris@zankel.net>
diff --git a/include/asm-xtensa/param.h b/include/asm-xtensa/param.h
index 6f28139..ce3a336 100644
--- a/include/asm-xtensa/param.h
+++ b/include/asm-xtensa/param.h
@@ -11,15 +11,13 @@
 #ifndef _XTENSA_PARAM_H
 #define _XTENSA_PARAM_H
 
-#include <asm/variant/core.h>
-
 #ifdef __KERNEL__
 # define HZ		100		/* internal timer frequency */
 # define USER_HZ	100		/* for user interfaces in "ticks" */
 # define CLOCKS_PER_SEC (USER_HZ)	/* frequnzy at which times() counts */
 #endif
 
-#define EXEC_PAGESIZE	(1 << XCHAL_MMU_MIN_PTE_PAGE_SIZE)
+#define EXEC_PAGESIZE	4096
 
 #ifndef NGROUPS
 #define NGROUPS		32