ANDROID: kconfig: Enable option needed for MTK desktop

MTK_TIMER is selected by ARCH_MEDIATEK. The commit enables
it in order to not alter the core when we enable
CONFIG_ARCH_MEDIATEK in vendor fragment.
It is also not directly settable due to visibility
condition "if COMPILE_TEST" not met thus selecting
it as a hidden config.

The GKI_HIDDEN_MTK_CONFIGS is enabled if ARM64 since
it is only applicable to Mediatek devices.

The commit is a followup after the
commit 3e1c1717 that was
reverted due to build failure.
The modification to the original one include:
- removing options that were converted to vendor modules in
the meantime
- removing the options that are not used on the MTK desktop
device.
The revert commit for reference:
450db842.

Bug: 432487220

Change-Id: Iac562e539063a59f3988e87a151251eb7554f964
Signed-off-by: Zyta Szpak <zyta@google.com>