LoongArch: vDSO: Remove --hash-style=sysv

Glibc added support for .gnu.hash in 2006 and .hash has been obsoleted
far before the first LoongArch CPU was taped.  Using --hash-style=sysv
might imply unaddressed issues and confuse readers.

Some architectures use an explicit --hash-style=both for vDSO here, but
DT_GNU_HASH has already been supported by Glibc and Musl and become the
de-facto standard of the distros when the first LoongArch CPU was taped.
So DT_HASH seems just wasting storage space for LoongArch.

Just drop the option and rely on the linker default, which is likely
"gnu" (Arch, Debian, Gentoo, LFS) on all LoongArch distros (confirmed on
Arch, Debian, Gentoo, and LFS; AOSC now defaults to "both" but it seems
just an oversight).

Following the logic of commit 48f64305 ("arm64/vdso: Remove
--hash-style=sysv").

Link: https://github.com/AOSC-Dev/aosc-os-abbs/pull/9796


Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>