gdb/s390: Correct recording of "store on condition" insns

gdb/s390: Correct recording of "store on condition" insns

The "store on condition" instructions STOC, STOCG, and STOCFH are recorded
as if their instruction formats resembled that of STG.  This is wrong,
usually resulting in "failed to record execution log" errors when trying
to record code with any of these instructions.

This patch fixes the recording of these instructions.

gdb/ChangeLog:

	PR tdep/26916
	* s390-tdep.c (s390_process_record): Fix recording of STOC, STOCG,
	and STOCFH.