octeontx2-af: Generate key field bit mask from KEX profile

Key Extraction(KEX) profile decides how the packet metadata such as
layer information and selected packet data bytes at each layer are
placed in MCAM search key. This patch reads the configured KEX profile
parameters to find out the bit position and bit mask for each field.
The information is used when programming the MCAM match data by SW
to match a packet flow and take appropriate action on the flow. This
patch also verifies the mandatory fields such as channel and DMAC
are not overwritten by the KEX configuration of other fields.

Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: Naveen Mamindlapalli <naveenm@marvell.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>