kbuild: replace sed with $(subst ) or $(patsubst )

For simple text replacement, it is better to use a built-in function
instead of sed if possible. You can save one process forking.

I do not mean to replace all sed invocations because GNU Make itself
does not support regular expression (unless you use guile).

I just replaced simple ones.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Documentation/devicetree/bindings/Makefile

@@ -48,7 +48,7 @@ define rule_chkdt
 	$(call cmd,mk_schema)
 endef
 
-DT_DOCS = $(shell $(find_cmd) | sed -e 's|^$(srctree)/||')
+DT_DOCS = $(patsubst $(srctree)/%,%,$(shell $(find_cmd)))
 
 override DTC_FLAGS := \
 	-Wno-avoid_unnecessary_addr_size \

Makefile

@@ -574,7 +574,7 @@ endif
 # Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
 # CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
 # and from include/config/auto.conf.cmd to detect the compiler upgrade.
-CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1 | sed 's/\#//g')
+CC_VERSION_TEXT = $(subst $(pound),,$(shell $(CC) --version 2>/dev/null | head -n 1))
 
 ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
 ifneq ($(CROSS_COMPILE),)