MIPS: don't use get_symbol_name() for section parsing. With s_change_section() later...

MIPS: don't use get_symbol_name() for section parsing.  With s_change_section() later calling obj_elf_section(), it seems better to pre-parse the section name by the same function that will be used there. This way no differences in what is accepted will result.

gas	* config/tc-mips.c (s_change_section): Use obj_elf_section_name to
	parse the section name.