MdeModulePkg/VariableLock: downgrade compatibility warnings to DEBUG_WARN

MdeModulePkg/VariableLock: downgrade compatibility warnings to DEBUG_WARN

Commit a18a9bde36d2 ("MdeModulePkg/Variable/RuntimeDxe: Restore Variable
Lock Protocol behavior", 2020-12-15), for bug 3111, added two such sets of
debug messages that:

(a) are relevant for developers,

(b) yet should not necessarily poke end-users, because no functionality
suffers in practice.

Both message sets are in function VariableLockRequestToLock(): the first
is a generic interface deprecation warning; the second is the
double-locking situation, which we permit for compatibility (return status
EFI_SUCCESS).

Both message sets should be emitted with the DEBUG_WARN mask, not the most
serious DEBUG_ERROR mask. On some platforms, the serial console carries
both terminal traffic, and grave (DEBUG_ERROR-only) log messages. On such
platforms, both message sets may be perceived as a nuisance by end-users,
as there is nothing they can do, and there's nothing they *should* do --
in practice, nothing malfunctions.

(Such a platform is ArmVirtQemu, built with "-D
DEBUG_PRINT_ERROR_LEVEL=0x80000000".)

Cc: Bret Barkelew <bret.barkelew@microsoft.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3410
Fixes: a18a9bde36d2ffc12df29cdced1efa1f8f9f2021
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20210521204037.11980-1-lersek@redhat.com>
Reviewed-by: Bret Barkelew <bret.barkelew@microsoft.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>