Always default to DWARF2 debugging for RX, even with -mas100-syntax

Always default to DWARF2 debugging for RX, even with -mas100-syntax

The RX port defaults to STABS when -mas100-syntax is used because
the AS100 assembler does not support some of the pseudo-ops used
by DWARF2 debug emission.  Since STABS is going to be deprecated
that has to change.  The following simply always uses DWARF2,
likely leaving -mas100-syntax broken when debug info is generated.

Can the RX port maintainer please sort out the situation?

2021-09-10  Richard Biener  <rguenther@suse.de>

	* config/rx/rx.h (PREFERRED_DEBUGGING_TYPE): Always define to
	DWARF2_DEBUG.