OvmfPkg/QemuVideoDxe: upgrade VERBOSE debug messages to INFO

In commit 5b2291f9567a ("OvmfPkg: QemuVideoDxe uses
MdeModulePkg/FrameBufferLib"), QemuVideoDxe was rebased to
FrameBufferBltLib.

The FrameBufferBltLib instance added in commit b1ca386074bd
("MdeModulePkg: Add FrameBufferBltLib library instance") logs many
messages on the VERBOSE level; for example, a normal boot with OVMF can
produce 500+ "VideoFill" messages, dependent on the progress bar, when the
VERBOSE bit is set in PcdDebugPrintErrorLevel. While FrameBufferBltLib is
certainly allowed to log such messages on the VERBOSE level, we should
separate those frequent messages from the (infrequent) ones produced by
QemuVideoDxe itself.

QemuVideoDxe logs VERBOSE messages in three locations (in two functions)
at the moment. All of them are infrequent: both QemuVideoBochsModeSetup()
and InstallVbeShim() are called from QemuVideoControllerDriverStart(),
that is, when a device is bound. Upgrade these messages to INFO level, so
that VERBOSE can be disabled in PcdDebugPrintErrorLevel -- perhaps
selectively for OvmfPkg/QemuVideoDxe -- without hiding these infrequent
messages.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>