feat(tbbr): update PK_DER_LEN for ECDSA P-384 keys

Adding the PK_DER_LEN option for 384 key size when adding ECDSA P384 key
support

Change-Id: I0f19aebad20d1c552976dc3c22ed396d79614769
Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
1 file changed