arc: Small data doesn't need fcommon option

arc: Small data doesn't need fcommon option

ARC backend is defaulting to -fcommon. This is not anylonger needed, remove it.

gcc/
2021-08-12  Claudiu Zissulescu  <claziss@synopsys.com>

	* common/config/arc/arc-common.c (arc_option_init_struct): Remove
	fno-common reference.
	* config/arc/arc.c (arc_override_options): Remove overriding of
	flag_no_common.

Signed-off-by: Claudiu Zissulescu <claziss@synopsys.com>