ppc: configs: Remove a few non-updated build configurations

In the cases of T2080RDB_SECURE_BOOT, T2080RDB_SRIO_PCIE_BOOT,
P2041RDB_SECURE_BOOT, P2041RDB_SRIO_PCIE_BOOT, P3041DS_SRIO_PCIE_BOOT
and P4080DS_SRIO_PCIE_BOOT while some forms of the board have been
migrated more fully to current build standards, these have not.  Remove
them.

Cc: Priyanka Jain <priyanka.jain@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>