MLK-20964-1: arm64: defconfig: Remove explicit RC_CORE=y

Since CONFIG_IR_GPIO_CIR=y depends on RC_CORE we shouldn't explicitly
define CONFIG_RC_CORE=y in defconfig, otherwise it generates a
difference between the output of "make savedefconfig" and the actual
defconfig.

Fixes: 35c88640 ("MLK-20946-3: arm64: defconfig: add IR support for imx8")

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Joakim Zhang <qiangqing.zhang@nxp.com>