The P2SB could get an invalid BAR from the BIOS, and that won't be fixed
up until pcibios_assign_resources(), which is an fs_initcall().

- Move p2sb_fs_init() to an fs_initcall_sync(). This is still early
  enough to avoid a race with any dependent drivers.

- Add a check for IORESOURCE_UNSET in p2sb_valid_resource() to catch
  unset BARs going forward.

- Return error values from p2sb_fs_init() so that the 'initcall_debug'
  cmdline arg provides useful data.
Signed-off-by: Ben Fradella <bfradell@netapp.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Klara Modin <klarasmodin@gmail.com>
Reviewed-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Link: https://lore.kernel.org/r/20240509164905.41016-1-bcfradella@proton.meReviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>