cmd/internal/obj/loong64: recheck jump offset boundary after auto-aligning loop heads

After the alignment of the loop header is performed, the offset of the checked
conditional branch instruction may overflow, so it needs to be checked again.

When checking whether the offset of the branch jump instruction overflows, it
can be classified and processed according to the range of the immediate field
of the specific instruction, which can reduce the introduction of unnecessary
jump instructions.

Fixes #61819

Change-Id: I772a5b5b8b8de21c78d7566be30be8ff65fdbce8
Reviewed-on: https://go-review.googlesource.com/c/go/+/519915


Reviewed-by: sophie zhao <zhaoxiaolin@loongson.cn>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Meidan Li <limeidan@loongson.cn>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Run-TryBot: qiu laidongfeng2 <2645477756@qq.com>
Reviewed-by: WANG Xuerui <git@xen0n.name>