Add BaseRiscVFpuLib.inf in SG2042.dsc

it is necessary to build SG2042.fv

Cc: dahogn <dahogn@hotmail.com>
Cc: caiyuqing379 <caiyuqing_hz@outlook.com>
Cc: meng-cz <mengcz1126@gmail.com>
Cc: USER0FISH <libing1202@outlook.com>
Signed-off-by: ZixuanDing <blacktang482@gmail.com>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>