ARM: 5734/1: arm: fix compilation of entry-common.S for older CPUs

Commit 181f817eaaca4c1f introduced some new code to entry-common.S
Sadly, this new code uses 'bx' instruction which is available only on
ARMv5 and higher CPUs. This causes following compilation errors when
building kernel for StrongARM (ARMv4):

arch/arm/kernel/entry-common.S: Assembler messages:
arch/arm/kernel/entry-common.S:129: Error: selected processor does not
support `bx ip'
arch/arm/kernel/entry-common.S:138: Error: selected processor does not
support `bx ip'

Fix these errors by using 'mov pc' instead of 'bx'.

Signed-off-by: Dmitry Artamonow <[e-mail]>
Acked-by: Uwe Kleine-König <[e-mail]>
Signed-off-by: Russell King <[e-mail]>

arch/arm/kernel/entry-common.S

···
 	cmp r0, r2
 	bne gnu_trace
 	ldmia sp!, {r0-r3, ip, lr}
-	bx ip
+	mov pc, ip
 
 gnu_trace:
 	ldr r1, [sp, #20]			@ lr of instrumented routine
···
 	mov lr, pc
 	mov pc, r2
 	ldmia sp!, {r0-r3, ip, lr}
-	bx ip
+	mov pc, ip
 
 ENTRY(mcount)
 	stmdb sp!, {r0-r3, lr}