powerpc/eeh: Avoid misleading message "EEH: no capable adapters found"

powerpc/eeh: Avoid misleading message "EEH: no capable adapters found"

Due to recent refactoring in EEH in:
commit be482d1a1cf4 ("powerpc/powernv: Rework EEH initialization on
powernv")
a misleading message was seen in the kernel message buffer:

[    0.108431] EEH: PowerNV platform initialized
[    0.589979] EEH: No capable adapters found

This happened due to the removal of the initialization delay for powernv
platform.

Even though the EEH infrastructure for the devices is eventually
initialized and still works just fine the eeh device probe step is
postponed in order to assure the PEs are created. Later
pnv_eeh_post_init does the probe devices job but at that point the
message was already shown right after eeh_init flow.

This patch introduces a new flag EEH_POSTPONED_PROBE to represent that
temporary state and avoid the message mentioned above and showing the
follow one instead:

[    0.107724] EEH: PowerNV platform initialized
[    4.844825] EEH: PCI Enhanced I/O Error Handling Enabled

Signed-off-by: Mauro S. M. Rodrigues <maurosr@linux.vnet.ibm.com>
Acked-by: Russell Currey <ruscur@russell.cc>
Tested-by:Venkat Rao B <vrbagal1@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>