testsuite: Verify r0-r3 are extended with CMSE

testsuite: Verify r0-r3 are extended with CMSE

Add regression test to the existing zero/sign extend tests for CMSE to
verify that r0, r1, r2 and r3 are properly extended, not just r0.

boolCharShortEnumSecureFunc test is done using -O0 to ensure the
instructions are in a predictable order.

gcc/testsuite/ChangeLog:

	* gcc.target/arm/cmse/extend-param.c: Add regression test. Add
	-fshort-enums.
	* gcc.target/arm/cmse/extend-return.c: Add -fshort-enums option.

Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>