MACsec: Fix policy configuration

MACsec: Fix policy configuration

macsec_validate variable was set incorrectly to FALSE(0) or TRUE(1)
instead of the enum validate_frames values (Disabled(0), Checked(1),
Strict(2). This ended up policy == SHOULD_SECURE to be mapped to
macsec_validate == Checked instead of Strict. This could have resulted
in unintended SecY forwarding of invalid packets rather than dropping
them.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>