[PATCH 3/5][Arm] New pattern for CSINC instructions

[PATCH 3/5][Arm] New pattern for CSINC instructions

This patch adds a new pattern, *thumb2_csinc, for generating CSINC
instructions. It also modifies an existing pattern, *thumb2_cond_arith, to
output CINC when the operation is an addition and TARGET_COND_ARITH is true.

gcc/ChangeLog:

	* config/arm/thumb2.md (*thumb2_csinc): New.
	(*thumb2_cond_arith): Generate CINC where possible.

gcc/testsuite/ChangeLog:

	* gcc.target/arm/csinc-1.c: New test.

Co-authored-by: Omar Tahir <omar.tahir@arm.com>