KVM: PPC: Use __func__ to get function's name

Prefer using '"%s...", __func__' to get current function's name in
output messages.

Signed-off-by: XueBing Chen <chenxuebing@jari.cn>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/13b2c857.beb.181725bad35.Coremail.chenxuebing@jari.cn