ARM: 8894/1: boot: Replace open-coded nop with macro

ARM: 8894/1: boot: Replace open-coded nop with macro

This open-coded nop as mov r0, r0 is a development history
artifact.

First commit 615e605fc8c4
("ARM: 6663/1: make Thumb2 kernel entry point more similar
to the ARM one") moved the code around so that the nops
would come before the conditional thumb instructions, as it
turned out that some boot loaders were patching the initial
nop instructions in the kernel. At this point it is clear
that all mov r0,r0 are open-coded nops.

Then commit ad26a2b543e3 ("ARM: add UEFI stub support")
moved things around and defined __nop for EFI support and
missed this open-coded nop.

commit 370f980978c4
("ARM: 8677/1: boot/compressed: fix decompressor header
layout for v7-M") makes all invocations of __nop be wide,
but that is fine, because this is what we want: the
mov r0,r0 is inside ifndef CONFIG_THUMB2_KERNEL.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Acked-by: Roy Franz <rfranz@marvell.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>