s390/vdso: drop '-fPIC' from LDFLAGS

s390/vdso: drop '-fPIC' from LDFLAGS

'-fPIC' as an option to the linker does not do what it seems like it
should. With ld.bfd, it is treated as '-f PIC', which does not make
sense based on the meaning of '-f':

  -f SHLIB, --auxiliary SHLIB Auxiliary filter for shared object symbol table

When building with ld.lld (currently under review in a GitHub pull
request), it just errors out because '-f' means nothing and neither does
'-fPIC':

  ld.lld: error: unknown argument '-fPIC'

'-fPIC' was blindly copied from CFLAGS when the vDSO stopped being
linked with '$(CC)', it should not be needed. Remove it to clear up the
build failure with ld.lld.

Fixes: 2b2a25845d53 ("s390/vdso: Use $(LD) instead of $(CC) to link vDSO")
Link: https://github.com/llvm/llvm-project/pull/75643
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Fangrui Song <maskray@google.com>
Link: https://lore.kernel.org/r/20240130-s390-vdso-drop-fpic-from-ldflags-v1-1-094ad104fc55@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>