LoongArch: Remove unused and incorrect "sge<u>_<X:mode><GPR:mode>" define_insn
If this insn is really used, we'll have something like
slti $r4,$r0,$r5
in the code. The assembler will reject it because slti wants 2
register operands and 1 immediate operand. But we've not got any bug
report for this, indicating this define_insn is unused at all.
Note that do_store_flag (in expr.cc) is already converting x >= 1 to
x > 0 unconditionally, so this define_insn is indeed unused and we can
just remove it.