soc: arm: nxp_imx: rt: Remove CONFIG_OCRAM_NOCACHE setting

Remove CONFIG_OCRAM_NOCACHE setting, as this is now possible to achieve
using devicetree linker regions, and there is no point in having a
specific Kconfig for one memory region on the RT series like this.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>