board: cssi: Initialise port F on MIAE

When equipped with the SRSA audio board, MIAE equipment
has an additional port called port F.

Initialise that port just like other ports of the board, so
that it is already configured when starting Linux kernel.

Signed-off-by: Hugo Dubois <hugo.dubois.ext@csgroup.eu>
Reviewed-by: CASAUBON Jean Michel <jean-michel.casaubon@csgroup.eu>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>