Makefile: use two double-quotations as a pair

Some editors such as Emacs can highlight source files.
But their parser algorithm is not perfect.

If you use one double-quotation alone, some editor cannot
handle it nicely and mark source lines as a string by mistake.

It is preferable to use two double-quotations as a pair.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/arch/blackfin/config.mk b/arch/blackfin/config.mk
index 35f8716..73fa798 100644
--- a/arch/blackfin/config.mk
+++ b/arch/blackfin/config.mk
@@ -14,9 +14,9 @@
 	$(shell awk '$$2 == "CONFIG_BFIN_CPU" { print $$3 }' \
 		$(src)include/configs/$(BOARD).h)
 else
-CONFIG_BFIN_CPU := $(strip $(subst ",,$(CONFIG_BFIN_CPU)))
+CONFIG_BFIN_CPU := $(strip $(CONFIG_BFIN_CPU:"%"=%))
 endif
-CONFIG_BFIN_BOOT_MODE := $(strip $(subst ",,$(CONFIG_BFIN_BOOT_MODE)))
+CONFIG_BFIN_BOOT_MODE := $(strip $(CONFIG_BFIN_BOOT_MODE:"%"=%))
 
 PLATFORM_RELFLAGS += -ffixed-P3 -fomit-frame-pointer -mno-fdpic
 PLATFORM_CPPFLAGS += -DCONFIG_BLACKFIN