staging: erofs: change 'unsigned' to 'unsigned int'

Fix coding style issue "Prefer 'unsigned int' to bare use of 'unsigned'"
detected by checkpatch.pl

Signed-off-by: Leon Imhof <leon.imhof@in.tum.de>
Reviewed-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>