arc: Fix cached to uncached moves.

arc: Fix cached to uncached moves.

We need an temporary register when moving data from a cached memory to
an uncached memory. Fix this issue and add a test for it.

gcc/
2020-12-29  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.c (prepare_move_operands): Use a temporary
	registers when we have cached mem-to-uncached mem moves.

gcc/testsuite/
2020-12-29  Vladimir Isaev  <isaev@synopsys.com>

	* gcc.target/arc/uncached-9.c: New test.

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