OvmfPkg: Sec: Fix SOURCE_DEBUG_ENABLE ASSERT()

OvmfPkg: Sec: Fix SOURCE_DEBUG_ENABLE ASSERT()

The update to the LocalApicLib instances to make sure the Local APIC is
initialized before use (SVN r18595 / git commit 6d72ff7d9daf) generates an
ASSERT() when SOURCE_DEBUG_ENABLE is enabled for OVMF.

The fix is to initialize the Local APIC Timer and mask it before
initializing the DebugAgent.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
[lersek@redhat.com: rewrap code comment, rewrap commit msg, add precise
 commit ref]

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18622 6f19259b-4bc3-4df7-8a09-765794883524