xtensa: fix build warning in 64-bit build environment

This fixes the following build warnings:

arch/xtensa/mm/misc.S: Assembler messages:
arch/xtensa/mm/misc.S:143: Warning: value 0xffffffff30000106 truncated to 0x30000106
arch/xtensa/mm/misc.S:197: Warning: value 0xffffffff30000106 truncated to 0x30000106
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

arch/xtensa/mm/misc.S

@@ -140,7 +140,7 @@ ENTRY(clear_user_page)
 
 	/* Setup a temporary DTLB with the color of the VPN */
 
-	movi	a4, -PAGE_OFFSET + (PAGE_KERNEL | _PAGE_HW_WRITE)
+	movi	a4, ((PAGE_KERNEL | _PAGE_HW_WRITE) - PAGE_OFFSET) & 0xffffffff
 	movi	a5, TLBTEMP_BASE_1			# virt
 	add	a6, a2, a4				# ppn
 	add	a2, a5, a3				# add 'color'
@@ -194,7 +194,7 @@ ENTRY(copy_user_page)
 	or	a9, a9, a8
 	slli	a4, a4, PAGE_SHIFT
 	s32i	a9, a5, PAGE_FLAGS
-	movi	a5, -PAGE_OFFSET + (PAGE_KERNEL | _PAGE_HW_WRITE)
+	movi	a5, ((PAGE_KERNEL | _PAGE_HW_WRITE) - PAGE_OFFSET) & 0xffffffff
 
 	beqz	a6, 1f