Extract rhs packing parameter struct into kai_common.h

Alias existing nxk/kxn packing parameter structs to new one.

To keep a consistent interface for the packing function(s) within a microkernel folder.

Signed-off-by: Michael Kozlov <michael.kozlov@arm.com>

Reviewed-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Reviewed-by: Michael Kozlov <michael.kozlov@arm.com>
Approved-by: Gian Marco Iodice <gianmarco.iodice@arm.com>