drivers: descend into sub directories only when it is necessary

- Descend into drivers/fpga/ only when CONFIG_FPGA=y
  - Descend into drivers/bios_emulator only when CONFIG_BIOSEMU=y

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

drivers/Makefile

@@ -1,8 +1,8 @@
-obj-y += bios_emulator/
+obj-$(CONFIG_BIOSEMU) += bios_emulator/
 obj-y += block/
 obj-$(CONFIG_BOOTCOUNT_LIMIT) += bootcount/
 obj-y += crypto/
-obj-y += fpga/
+obj-$(CONFIG_FPGA) += fpga/
 obj-y += hwmon/
 obj-y += misc/
 obj-y += pcmcia/

drivers/bios_emulator/Makefile

@@ -2,7 +2,7 @@ X86DIR  = x86emu
 
 $(shell mkdir -p $(obj)$(X86DIR))
 
-obj-$(CONFIG_BIOSEMU)	= atibios.o biosemu.o besys.o bios.o \
+obj-y = atibios.o biosemu.o besys.o bios.o \
 	$(X86DIR)/decode.o \
 	$(X86DIR)/ops2.o \
 	$(X86DIR)/ops.o \

drivers/fpga/Makefile

@@ -5,7 +5,6 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-ifdef CONFIG_FPGA
 obj-y += fpga.o
 obj-$(CONFIG_FPGA_SPARTAN2) += spartan2.o
 obj-$(CONFIG_FPGA_SPARTAN3) += spartan3.o
@@ -19,4 +18,3 @@ obj-$(CONFIG_FPGA_ACEX1K) += ACEX1K.o
 obj-$(CONFIG_FPGA_CYCLON2) += cyclon2.o
 obj-$(CONFIG_FPGA_STRATIX_II) += stratixII.o
 endif
-endif