powerpc/eeh: Refactor EEH PE reset functions

eeh_pe_reset and eeh_reset_pe are two different functions in the same
file which do mostly the same thing.  Not only is this confusing, but
potentially causes disrepancies in functionality, notably eeh_reset_pe
as it does not check return values for failure.

Refactor this into the following:

 - eeh_pe_reset(): stays as is, performs a single operation, exported
 - eeh_pe_reset_full(): new, full reset process that calls eeh_pe_reset()
 - eeh_reset_pe(): removed and replaced by eeh_pe_reset_full()
 - eeh_reset_pe_once(): removed

Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>