spi: mediatek: fix wrong error return value on probe

Commit adcbcfea ("spi: mediatek: fix spi clock usage error")
added a new sel_clk but introduced bugs in the error paths since
the wrong struct clk pointers are passed to PTR_ERR().

Fixes: adcbcfea ("spi: mediatek: fix spi clock usage error")
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>