arm: socfpga: Use CMD_FS_GENERIC

arm: socfpga: Use CMD_FS_GENERIC

Enable and use the CONFIG_CMD_FS_GENERIC to avoid hard-coding the
filesystem type into the environment.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Chin Liang See <[email protected]>
Cc: Dinh Nguyen <[email protected]>
Cc: Albert Aribaud <[email protected]>
Cc: Tom Rini <[email protected]>
Cc: Wolfgang Denk <[email protected]>
Cc: Pavel Machek <[email protected]>
Acked-by: Pavel Machek <[email protected]>