sf: nr_sectors -> n_sectors

sf: nr_sectors -> n_sectors

Rename nr_sectors as n_sectors to sync with Linux.

Cc: Bin Meng <[email protected]>
Cc: York Sun <[email protected]>
Cc: Vignesh R <[email protected]>
Cc: Mugunthan V N <[email protected]>
Cc: Michal Simek <[email protected]>
Signed-off-by: Jagan Teki <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Reviewed-by: Jagan Teki <[email protected]>
Tested-by: Jagan Teki <[email protected]>
Reviewed-by: Siva Durga Prasad Paladugu <[email protected]>