cmake: lld: Remove duplicate -fuse-ld=lld

-fuse-ld=lld is currently specified twice through the baremetal property
(in cmake/linker/lld/linker_flags.cmake) and TOOLCHAIN_LD_FLAGS (in
cmake/linker/lld/target.cmake). This doesn't really harm anything as
it isn't duplicated on the link line (and specifying it multiple times
wouldn't hurt even if it was), but it also doesn't really help anything.

-fuse-ld isn't baremetal-specific and setting it via TOOLCHAIN_LD_FLAGS
will cover this case anyway, so remove this duplicate.

Signed-off-by: Jonathon Penix <jpenix@quicinc.com>