[ARM] Remove old binutils compatibility.

Old binutils (without .incbin) had the idea that a certain assembler
instruction was illegal.  binutils has since been fixed to allow it.

arch/arm/kernel/entry-header.S

@@ -63,13 +63,7 @@
 #define S_OFF		8
 
 	.macro	set_cpsr_c, reg, mode
-#if 1
-	/* broken binutils */
-	mov	\reg, \mode
-	msr	cpsr_c, \reg
-#else
 	msr	cpsr_c, \mode
-#endif
 	.endm
 
 	.macro	disable_irq, temp