tic54x: rename typedef of struct symbol_

tic54x: rename typedef of struct symbol_

generic gas code has a struct symbol, and tic54x typedefs a struct to symbol.
This seems at least rather confusing, and it seems like target specific headers
shouldn't  put such generic names in the global namespace preventing other
generic code from using them.

opcodes/ChangeLog:

2016-05-23  Trevor Saunders  <[email protected]>

	* tic54x-dis.c (sprint_mmr): Adjust.
	* tic54x-opc.c: Likewise.

gas/ChangeLog:

2016-05-23  Trevor Saunders  <[email protected]>

	* config/tc-tic54x.c (tic54x_mmregs): Adjust.
	(md_begin): Likewise.
	(encode_condition): Likewise.
	(encode_cc3): Likewise.
	(encode_cc2): Likewise.
	(encode_operand): Likewise.
	(tic54x_undefined_symbol): Likewise.

include/ChangeLog:

2016-05-23  Trevor Saunders  <[email protected]>

	* opcode/tic54x.h (struct symbol_): typedef to tic54x_symbol instead of
	plain symbol.