LoongArch: Fix "-mexplict-relocs=none -mcmodel=medium" producing %call36 when the assembler does not support it

Even if !HAVE_AS_SUPPORT_CALL36, const_call_insn_operand should still
return false when -mexplict-relocs=none -mcmodel=medium to make
loongarch_legitimize_call_address emit la.local or la.global.

gcc/ChangeLog:

	* config/loongarch/predicates.md (const_call_insn_operand):
	Remove buggy "HAVE_AS_SUPPORT_CALL36" conditions.  Change "1" to
	"true" to make the coding style consistent.