spi: mt7621: Remove 'clk' from 'struct mt7621_spi'

The 'clk' field in 'struct mt7621_spi' is useless, remove it.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/76ed0ef91479498b9a2d5ef539f80851cffdb4ea.1661599671.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Mark Brown <broonie@kernel.org>