gas: sframe: avoid creating more symbols than necessary for FRE offset

gas: sframe: avoid creating more symbols than necessary for FRE offset

Each SFrame FDE contains an offset to the start of its respective SFrame
FREs in the sfde_func_start_fre_off field.  To generate this offset,
fre_symbols[] array is being used.  The number of elements of this array
is currently set to the total number of SFrame FREs in the entire SFrame
section.  This is more than unnecessary.  We only need to track as many
points as the number of SFrame FDEs.

gas/
	* gen-sframe.c (output_sframe_internal):  Size fde_fre_symbols
	with the number of SFrame FDEs.