LoongArch: vDSO: Remove -nostdlib complier flag

Since $(LD) is directly used, hence -nostdlib is unneeded, MIPS has
removed this, we should remove it too.

bdbf2038 ("MIPS: VDSO: remove -nostdlib compiler flag").

In fact, other architectures also use $(LD) now.

fe00e50b ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to link VDSO")
691efbed ("arm64: vdso: use $(LD) instead of $(CC) to link VDSO")
2ff90699 ("MIPS: VDSO: Use $(LD) instead of $(CC) to link VDSO")
2b2a2584 ("s390/vdso: Use $(LD) instead of $(CC) to link vDSO")

Cc: stable@vger.kernel.org
Reviewed-by: Yanteng Si <siyanteng@cqsoftware.com.cn>
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>