Some Makefiles use ccflags-y, but it is not actually supported.
Support ccflags-y, asflags-y, cppflags-y, and ldflags-y like Linux.

Remove the workaround in drivers/pci/Makefile.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>