powerpc/pseries/hvcserver: Fix endian issue in hvcs_get_partner_info

A buffer returned by H_VTERM_PARTNER_INFO contains device information
in big endian format, causing problems for little endian architectures.
This patch ensures that they are in cpu endian.

Signed-off-by: Thomas Falcon <tlfalcon@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>