util: use void * instead of byte * for util_copy_rect in u_format.h

util: use void * instead of byte * for util_copy_rect in u_format.h

As ubyte comes from p_compiler.h,  so do not use it,
and the code calles util_copy_rect may use args with type uint8_t*, ubyte* or unsigned char*,
so use the type void* that consistence with memcpy

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19676>