ARM: bcm2708: PL01X debug include was moved into arch/arm/include/debug/

This patch fixes a compilation error:
In file included from arch/arm/kernel/head.S:27:0:
arch/arm/mach-bcm2708/include/mach/debug-macro.S:22:38: fatal error: asm/hardware/debug-pl01x.S: No such file or directory