aarch64: Fix failure in cmpimm_branch_1.c

aarch64: Fix failure in cmpimm_branch_1.c

gcc.target/aarch64/cmpimm_branch_1.c started failing after Bernd's
fix to make combine take the costs of jumps into account
(g:391500af1932e696a007).  This is because the rtx costs
of *compare_condjump<GPI:mode> were higher than the costs
of the instructions it combines.

2020-01-27  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/aarch64.c (aarch64_if_then_else_costs): Match
	jump conditions for *compare_condjump<GPI:mode>.