erofs: remove redundant erofs_fs_type declaration in super.c

As erofs_fs_type has been declared in internal.h, there is no use to
declare repeatedly in super.c.

Signed-off-by: Ferry Meng <mengferry@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
eviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230815094849.53249-3-mengferry@linux.alibaba.com


Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>