misc/pvpanic: Make 'pvpanic_probe()' resource managed

Simplify code and turn 'pvpanic_probe()' into a managed resource version.
This simplify callers that don't need to do some clean-up on error in the
probe and on remove.

Update pvpanic-mmio.c and pvpanic-pci.c accordingly.

'pvpanic_remove()' don't need to be exported anymore.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/9212cdc8c1e5c187a2f1129a6190085c2a10d28a.1621665058.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>