LoongArch: Fix instruction immediate bug caused by sign-extend

For extreme code mode, the instruction sequences is
    pcalau12i $t0, hi20
    addi.d $t1, $zero, lo12
    lu32i.d $t1, lo20
    lu52i.d $t1, hi12
    add.d $t1, $t0, $t1

If lo12 > 0x7ff, hi20 need to add 0x1, lo20 need to sub 0x1.
If hi20 > 0x7ffff, lo20 need to add 0x1.

bfd/ChangeLog:

	* elfnn-loongarch.c (RELOCATE_CALC_PC32_HI20): Redefined.
	(RELOCATE_CALC_PC64_HI32): Redefined.
1 file changed