tilegx: Unbreak build

tilegx: Unbreak build

../../gcc/config/tilegx/tilegx.md:4109:1: ambiguous attribute 'n'; could be '1' (via 'I124MODE:n') or '4' (via 'I48MODE:n')
../../gcc/config/tilegx/tilegx.md:4109:1: ambiguous attribute 'n'; could be '1' (via 'I124MODE:n') or '' (via 'I48MODE:n')
../../gcc/config/tilegx/tilegx.md:4109:1: ambiguous attribute 'n'; could be '2' (via 'I124MODE:n') or '4' (via 'I48MODE:n')
../../gcc/config/tilegx/tilegx.md:4109:1: ambiguous attribute 'n'; could be '2' (via 'I124MODE:n') or '' (via 'I48MODE:n')
../../gcc/config/tilegx/tilegx.md:4109:1: ambiguous attribute 'n'; could be '4' (via 'I124MODE:n') or '' (via 'I48MODE:n')

The insn name already uses <I124MODE:n> explicitly, just the preparation
stmts don't, and as it creates a I124MODE lowpart subreg of a word mode
register, <I124MODE:n> seems obviously correct.

2020-05-02  Jakub Jelinek  <jakub@redhat.com>

	* config/tilegx/tilegx.md
	(insn_stnt<I124MODE:n>_add<I48MODE:bitsuffix>): Use <I124MODE:n>
	rather than just <n>.