spi: hisi-kunpeng: Delete the dump interface of data registers in debugfs

Due to the reading of FIFO during the dump of data registers in
debugfs, if SPI transmission is in progress, it will be affected
and may result in transmission failure. Therefore, the dump
interface of data registers in debugfs is removed.

Fixes: 2b2142f2

 ("spi: hisi-kunpeng: Add debugfs support")
Signed-off-by: Devyn Liu <liudingyuan@huawei.com>
Reviewed-by: Jay Fang <f.fangjian@huawei.com>
Link: https://lore.kernel.org/r/20240416015839.3323398-1-liudingyuan@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>