cmake: Fix dependency issue in x86 build scripts
cmake: Fix dependency issue in x86 build scripts

Incremental builds have been broken in x86 due to a misconfigured
dependency. mmu_tables.bin is always generated, even for "nothing to
do" builds.

We fix this by removing the stray dependency on user_mmu_tables.bin
when not CONFIG_X86_KPTI.

Steps to reproduce:

Build any sample twice with qemu_x86 and observe that the second build
regenerates mmu_tables.bin.

Signed-off-by: Sebastian Bøe <edee888afd63e94916688495334700803eba20a0@nordicsemi.no>

ldts/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,Vudentz/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,galak/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,ldts/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,nashif/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,Vudentz/zephyr