gas: Test predicate whether SFrame RA tracking is used

gas: Test predicate whether SFrame RA tracking is used

The existence of the macro SFRAME_FRE_RA_TRACKING only ensures the
existence of the macro SFRAME_CFA_RA_REG and the predicate function
sframe_ra_tracking_p. It does not indicate whether SFrame RA tracking
is actually used.

Test the return value of the SFrame RA tracking predicate function
sframe_ra_tracking_p to determine whether RA tracking is used.

This aligns the logic in functions get_fre_num_offsets and
output_sframe_row_entry to the one used in all other places.

gas/
	* gen-sframe.c (get_fre_num_offsets, output_sframe_row_entry):
	Test predicate to determine whether SFrame RA tracking is used.

Signed-off-by: Jens Remus <jremus@linux.ibm.com>