ARM: socfpga: do not add board directory to header search path

The compiler option "-Iboard/$(VENDOR)/$(BOARD)" just exists here
for iocsr_config.c to be able to include iocsr_config.h.

Use "..." instead of <...> to include a header in the same directory.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/arm/cpu/armv7/socfpga/config.mk

@@ -6,6 +6,3 @@
 ifndef CONFIG_SPL_BUILD
 ALL-y	+= u-boot.img
 endif
-
-# Added for handoff support
-PLATFORM_RELFLAGS += -Iboard/$(VENDOR)/$(BOARD)