radv: fix getting the index type size for uint8_t
16-bit and 32-bit values match hardware values but 8-bit doesn't.
This fixes dEQP-VK.pipeline.input_assembly.* with 8-bit index.
Fixes: 372c3dcf ("radv: implement VK_EXT_index_type_uint8") Signed-off-by: Samuel Pitoiset samuel.pitoiset@gmail.com