Hisilicon/RX8900RealTimeClockLib: drop LibRtcVirtualNotifyEvent

The RealTimeClockLib class header in edk2 mistakenly declares a function
called LibRtcVirtualNotifyEvent(). No component ever calls this function
crossing module boundaries; all RealTimeClockLib instances in edk2 and
edk2-platforms are supposed to register (and do register) their
SetVirtualAddressMap() notification functions.

In particular, RX8900RealTimeClockLib *itself* doesn't even use
LibRtcVirtualNotifyEvent() -- the function is defined with an empty body,
clearly in an understandable, but misguided, attempt, to conform to the
(bogus) library interface. Remove the function.

Note that this patch is *untestable* in edk2-platforms (and in
edk2-non-osi too), because no platform consumes RX8900RealTimeClockLib --
worse, there hasn't been a single consumer since the introduction of the
lib instance in commit de704335 ("Silicon/Hisilicon: Add
RX8900RealTimeClockLib", 2020-05-20).

Normally this would nominate RX8900RealTimeClockLib to the axe, but commit
de704335 said, "There are some boards base on D06, but use RX8900 RTC,
so upstream the RX8900RealTimeClockLib", so I guess there might be
out-of-tree / proprietary consumers. Quite unfortunate.

Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Wenyi Xie <xiewenyi2@huawei.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=4564


Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>