hppa: Fix bug in atomic_storedi_1 pattern

The first alternative stores the floating-point status register
in the destination.  It should store zero.  We need to copy %fr0
to another floating-point register to initialize it to zero.

2024-02-01  John David Anglin  <danglin@gcc.gnu.org>

gcc/ChangeLog:

	* config/pa/pa.md (atomic_storedi_1): Fix bug in
	alternative 1.