mtd: rawnand: meson: stop supporting legacy clocks

meson NFC driver only uses common clock interfaces, which triggers kernel test
robot errors when using legacy clocks with HAVE_LEGACY_CLK on.

Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Liang Yang <liang.yang@amlogic.com>
[miquel.raynal@bootlin.com: Rephrase the commit log]
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220907080405.28240-6-liang.yang@amlogic.com