powerpc/probes: Remove ppc_opcode_t

ppc_opcode_t is just an u32. There is no point in hiding u32
behind such a typedef. Remove it.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b2d762191b095530789ac8b71b167c6740bb6aed.1657205708.git.christophe.leroy@csgroup.eu