firmware_loader: move firmware/ to drivers/base/firmware_loader/builtin/

Currently, the 'firmware' directory only contains a single Makefile
to embed extra firmware into the kernel.

Move it to the more relevant place.

Signed-off-by: Masahiro Yamada <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Makefile

···
 ifeq ($(KBUILD_EXTMOD),)
 # Objects we will link into vmlinux / subdirs we need to visit
 init-y		:= init/
-drivers-y	:= drivers/ sound/ firmware/
+drivers-y	:= drivers/ sound/
 net-y		:= net/
 libs-y		:= lib/
 core-y		:= usr/

drivers/base/firmware_loader/Makefile

···
 obj-$(CONFIG_FW_LOADER)	+= firmware_class.o
 firmware_class-objs := main.o
 firmware_class-$(CONFIG_FW_LOADER_USER_HELPER) += fallback.o
+
+obj-y += builtin/