bug.h: Fix up powerpc build regression.

The asm-generic/bug.h __ASSEMBLY__ guarding is completely bogus, which
tripped up the powerpc build when the kernel.h include was added:

	In file included from include/asm-generic/bug.h:5:0,
			 from arch/powerpc/include/asm/bug.h:127,
			 from arch/powerpc/kernel/head_64.S:31:
	include/linux/kernel.h:44:0: warning: "ALIGN" redefined [enabled by default]
	include/linux/linkage.h:57:0: note: this is the location of the previous definition
	include/linux/sysinfo.h: Assembler messages:
	include/linux/sysinfo.h:7: Error: Unrecognized opcode: `struct'
	include/linux/sysinfo.h:8: Error: Unrecognized opcode: `__kernel_long_t'

Moving the __ASSEMBLY__ guard up and stashing the kernel.h include under
it fixes this up, as well as covering the case the original fix was
attempting to handle.

Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>