OvmfPkg/SataControllerDxe: log informative message at DEBUG_INFO level

OvmfPkg/SataControllerDxe: log informative message at DEBUG_INFO level

When a UEFI_DRIVER attempts to open a protocol interface with BY_DRIVER
attribute that it already has open with BY_DRIVER attribute,
OpenProtocol() returns EFI_ALREADY_STARTED. This is not an error. The
UEFI-2.7 spec currently says,

> EFI_ALREADY_STARTED -- Attributes is BY_DRIVER and there is an item on
>                        the open list with an attribute of BY_DRIVER
>                        whose agent handle is the same as AgentHandle.

(In fact it is so much an expected condition that recent USWG Mantis
ticket <https://mantis.uefi.org/mantis/view.php?id=1815> will codify its
additional edk2-specific behavior, namely to output the protocol interface
at once.)

Downgrade the log mask for this one condition to DEBUG_INFO, in
SataControllerStart(). This will match the log mask of the other two
informative messages in this function, "SataControllerStart START", and
"SataControllerStart END status = %r" (at which point Status can only be
EFI_SUCCESS).

Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>