LoongArch: Fix the "%t" modifier handling for (const_int 0)

LoongArch: Fix the "%t" modifier handling for (const_int 0)

This modifier is intended to output $r0 for (const_int 0), but the
logic:

GET_MODE (op) != TImode || (op != CONST0_RTX (TImode) && code != REG)

will reject (const_int 0) because (const_int 0) actually does not have
a mode and GET_MODE will return VOIDmode for it.

Use reg_or_0_operand instead to fix the issue.

gcc/ChangeLog:

	* config/loongarch/loongarch.cc (loongarch_print_operand): Call
	reg_or_0_operand for checking the sanity of %t.