MIPS: generic: Include asm/bootinfo.h for plat_fdt_relocated()

MIPS: generic: Include asm/bootinfo.h for plat_fdt_relocated()

arch/mips/generic/init.c provides an implementation of the
plat_fdt_relocated() function, but doesn't include the asm/bootinfo.h
header which declares it. This leads to a warning from sparse:

arch/mips/generic/init.c:94:13: warning: symbol 'plat_fdt_relocated' was
  not declared. Should it be static?

Fix this by including asm/bootinfo.h to get the declaration of
plat_fdt_relocated(). We also #ifdef our definition of
plat_fdt_relocated() such that it is only provided when
CONFIG_RELOCATABLE is set, matching the header & avoiding the redundant
function for non-relocatable kernels.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: trivial@kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17166/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>