ANDROID: turn CONFIG_EXPERT for microdroid kernels

This is the preparation for turning off other CONFIG_* which are not
exposed unless CONFIG_EXPERT.

The actual (automatic) changes made to .config are as follows:

* CONFIG_NAMESPACES is removed. This is fine, because it was just a
  menuconfig for CONFIG_[UTS|TIME|USER|PID|NET]_NS, any of which wasn't
turned on for Android/Microdroid. Mount namespace which we use is
built-in.

* CONFIG_DEBUG_MEMORY_INIT is removed. This is also fine because this is
  excertized only via the mminit_loglevel param. Microdroid is not using
this.

* CONFIG_PCIE_BUS_DEFAULT is set to y. This isn't harmful, but will be
  removed in a follow-up change together with other PCIE configs.

Bug: 407854766
Test: run Microdroid with the new kernel
Change-Id: I29afcb42ebd6d6e09c6cb14bd824b9afcf77718d
Signed-off-by: Jiyong Park <jiyong@google.com>