mtd: rawnand: mtk: Use helper function devm_clk_get_enabled()

Since commit 7ef9651e ("clk: Provide new devm_clk helpers for prepared
and enabled clocks"), devm_clk_get() and clk_prepare_enable() can now be
replaced by devm_clk_get_enabled() when driver enables (and possibly
prepares) the clocks for the whole lifetime of the device. Moreover, it is
no longer necessary to unprepare and disable the clocks explicitly, so drop
the label "clk_disable". And both mtk_nfc_enable_clk() and
mtk_nfc_disable_clk() now have a single user, which is the resume or
suspend callback, so drop this two helper function and just move related
operations in the resume or suspend function.

Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Li Zetao <lizetao1@huawei.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230821031737.1973183-8-lizetao1@huawei.com