powerpc/configs: Merge pseries_defconfig and pseries_le_defconfig

These two configs should be identical with the exception of big or little
endian.

The big endian version has XMON_DEFAULT turned on while the little endian
has XMON_DEFAULT not set. It makes the most sense for defconfigs not to use
xmon by default, production systems should get back up as quickly as
possible, not sit in xmon.

In the event debugging is required, the option can be enabled or xmon=on
can be specified on commandline.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>