Fix read-after-free error in readelf when processing multiple, relocated sections...

Fix read-after-free error in readelf when processing multiple, relocated sections in an MSP430 binary.

	PR binutils/21139
	* readelf.c (target_specific_reloc_handling): Add num_syms
	parameter.  Check for symbol table overflow before accessing
	symbol value.  If reloc pointer is NULL, discard all saved state.
	(apply_relocations): Pass num_syms to target_specific_reloc_handling.
	Call target_specific_reloc_handling with a NULL reloc pointer
	after processing all of the relocs.