kbuild: rename OBJCFLAGS to OBJCOPYFLAGS

Rename OBJCFLAGS to OBJCOPYFLAGS beforehand to use
"cmd_objcopy" in scripts/Makefile.lib in an upcoming commit.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/arch/arm/config.mk b/arch/arm/config.mk
index 98c1253..8a65c34 100644
--- a/arch/arm/config.mk
+++ b/arch/arm/config.mk
@@ -108,7 +108,7 @@
 
 # limit ourselves to the sections we want in the .bin.
 ifdef CONFIG_ARM64
-OBJCFLAGS += -j .text -j .rodata -j .data -j .u_boot_list -j .rela.dyn
+OBJCOPYFLAGS += -j .text -j .rodata -j .data -j .u_boot_list -j .rela.dyn
 else
-OBJCFLAGS += -j .text -j .rodata -j .hash -j .data -j .got.plt -j .u_boot_list -j .rel.dyn
+OBJCOPYFLAGS += -j .text -j .rodata -j .hash -j .data -j .got.plt -j .u_boot_list -j .rel.dyn
 endif