ARM: fix build error in arch/arm/kernel/process.c

/tmp/ccJ3ssZW.s: Assembler messages:
/tmp/ccJ3ssZW.s:1952: Error: can't resolve `.text' {.text section} - `.LFB1077'

This is caused because:

	.section .data
	.section .text
	.section .text
	.previous

does not return us to the .text section, but the .data section; this
makes use of .previous dangerous if the ordering of previous sections
is not known.

Fix up the other users of .previous; .pushsection and .popsection are
a safer pairing to use than .section and .previous.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/assembler.h

@@ -149,10 +149,10 @@
 
 #define USER(x...)				\
 9999:	x;					\
-	.section __ex_table,"a";		\
+	.pushsection __ex_table,"a";		\
 	.align	3;				\
 	.long	9999b,9001f;			\
-	.previous
+	.popsection
 
 /*
  * SMP data memory barrier
@@ -193,10 +193,10 @@
 	.error	"Unsupported inc macro argument"
 	.endif
 
-	.section __ex_table,"a"
+	.pushsection __ex_table,"a"
 	.align	3
 	.long	9999b, \abort
-	.previous
+	.popsection
 	.endm
 
 	.macro	usracc, instr, reg, ptr, inc, cond, rept, abort
@@ -234,10 +234,10 @@
 	.error	"Unsupported inc macro argument"
 	.endif
 
-	.section __ex_table,"a"
+	.pushsection __ex_table,"a"
 	.align	3
 	.long	9999b, \abort
-	.previous
+	.popsection
 	.endr
 	.endm