spi: mt7621: Use the devm_clk_get_enabled() helper to simplify error handling

The devm_clk_get_enabled() helper:
   - calls devm_clk_get()
   - calls clk_prepare_enable() and registers what is needed in order to
     call clk_disable_unprepare() when needed, as a managed resource.

This helper is well suited for cases where the clock would be kept
prepared or enabled for the whole lifetime of the driver.

This simplifies the error handling a lot.

The order between spi_unregister_controller() (in the remove function) and
the clk_disable_unprepare() (now handle by a  managed resource) is kept
the same.
(see commit 46b5c4fb ("spi: mt7621: Don't leak SPI master in probe
error path") to see why it matters)

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/05a7fd22719008c8a905d6328aa9548ce40f2a7a.1661599671.git.christophe.jaillet@wanadoo.fr


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