s390/vdso: remove -nostdlib compiler flag

s390/vdso: remove -nostdlib compiler flag

The -nostdlib option requests the compiler to not use the standard
system startup files or libraries when linking. It is effective only
when $(CC) is used as a linker driver.

Since commit 2b2a25845d53 ("s390/vdso: Use $(LD) instead of $(CC) to
link vDSO"), $(LD) is directly used, hence -nostdlib is unneeded.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20211107162111.323701-1-masahiroy@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>