c4x.md: Fix minor formatting problems.

c4x.md: Fix minor formatting problems.

	* config/c4x/c4x.md: Fix minor formatting problems.  Update docs.
	(*b, *b_rev, *b_noov, *b_noov_rev, *db,
	decrement_and_branch_until_zero, rptb_end): Use c4x_output_cbranch
	to output the instruction sequences.
	(rpts): Delete.
	(rptb_top): Provide alternatives to use any register or memory
	for loop counter.
	(rptb_end):  Emit use of operands rather than assigning them
	explicitly to the RS and RE registers.

From-SVN: r23880