hikey: Remove unnecessary code

hikey: Remove unnecessary code

PLATFORM_LINKER_FORMAT
and
PLATFORM_LINKER_ARCH
defines are removed from
plat/hisilicon/hikey/include/platform_def.h
since there are already defined in
include/plat/common/common_def.h
which is included by
plat/hisilicon/hikey/hikey_def.h
which is included by
plat/hisilicon/hikey/include/platform_def.h

The line
$(eval $(call FIP_ADD_IMG,SCP_BL2,--scp-fw))
is removed from
plat/hisilicon/hikey/platform.mk
to clear the warning below:

Makefile:544: warning: overriding commands for target `check_SCP_BL2'
plat/hisilicon/hikey/platform.mk:19: warning: ignoring old commands for target `check_SCP_BL2'

$(eval $(call FIP_ADD_IMG,SCP_BL2,--scp-fw))
already exists in
Makefile
and applies to plat hikey so is redundant in
plat/hisilicon/hikey/platform.mk

Signed-off-by: Victor Chong <victor.chong@linaro.org>