config/ppc: ignore GCC 11 psabi warnings

config/ppc: ignore GCC 11 psabi warnings

Suppress the gcc warning "note: the layout of aggregates containing
vectors with 4-byte alignment has changed in GCC 5" on POWER systems
by setting "-Wno-psabi".  Warning was originally added to gcc in
commit https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=9832651 to warn
of the vector alignment changes introduced in GCC 5.  Older gcc
versions forced vector alignment to 16 bytes due to requirements for
POWER 6 and earlier CPUs, but these restrictions don't apply to CPUs
supported by DPDK.

Bugzilla ID: 739
Cc: stable@dpdk.org
Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>