erofs: kill verbose debug info in erofs_fill_super

As Christoph said [1], "That is some very verbose
debug info.  We usually don't add that and let
people trace the function instead. "

[1] https://lore.kernel.org/r/20190829101545.GC20598@infradead.org/


Reported-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190904020912.63925-15-gaoxiang25@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>