radv: enable the trap handler and configure the shader exceptions

When TRAP_PRESENT is not enabled, all traps and exceptions are ignored.
Only EXCP_EN.mem_viol is currently supported because the other
exceptions have to be tested/validated first.

EXCP_EN.mem_viol is used to detect any sort of invalid memory
access like VM fault. When a memory violation is reported, the
hw jumps to the trap handler.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6384>