gallium/swr: use ElementCount type arguments for getSplat()

Reviewed-by: Alok Hota <alok.hota@intel.com>

In LLVM11, ConstantVector::getSplat() function definition
has changed and the first function argument has now ElementCount type.

Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4188>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4188>
4 files changed