clk: imx: fix Kconfig warning for i.MX SCU clk

clk: imx: fix Kconfig warning for i.MX SCU clk

A previous patch introduced a harmless randconfig warning:

WARNING: unmet direct dependencies detected for MXC_CLK_SCU
  Depends on [n]: COMMON_CLK [=y] && ARCH_MXC [=n] && IMX_SCU [=y] && HAVE_ARM_SMCCC [=y]
  Selected by [m]:
  - CLK_IMX8QXP [=m] && COMMON_CLK [=y] && (ARCH_MXC [=n] && ARM64 [=y] || COMPILE_TEST [=y]) && IMX_SCU [=y] && HAVE_ARM_SMCCC [=y]

Since the symbol is now hidden and only selected by other symbols,
just remove the dependencies and require the other drivers to
get it right.

Fixes: 6247e31b7530 ("clk: imx: scu: fix MXC_CLK_SCU module build break")
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20201230155244.981757-1-arnd@kernel.org
Signed-off-by: Stephen Boyd <sboyd@kernel.org>