aesni_gcm: fix supported key sizes
aesni_gcm: fix supported key sizes

AES-GCM PMD only supports 128-bit keys, but not 192 and 256,
which the capabilities structure was reporting.

Fixes: 26c2e4ad5ad4 ("cryptodev: add capabilities discovery")

Signed-off-by: Pablo de Lara <28355d9cfe41bb8148aea0fb24f47aae8f4217a1@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk