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>
diff --git a/arch/arm/lib/backtrace.S b/arch/arm/lib/backtrace.S
index aaf7220..a673297 100644
--- a/arch/arm/lib/backtrace.S
+++ b/arch/arm/lib/backtrace.S
@@ -110,13 +110,13 @@
 ENDPROC(__backtrace)
 ENDPROC(c_backtrace)
 		
-		.section __ex_table,"a"
+		.pushsection __ex_table,"a"
 		.align	3
 		.long	1001b, 1006b
 		.long	1002b, 1006b
 		.long	1003b, 1006b
 		.long	1004b, 1006b
-		.previous
+		.popsection
 
 #define instr r4
 #define reg   r5