irqchip/gic-v3: Remove unused register definition

[maz: The GICv3 spec has evolved quite a bit since the draft the Linux
driver was written against, and some register definitions are simply gone]

As per the GICv3 specification, GIC{D,R}_SEIR are not assigned and the
locations (0x0068) are actually Reserved. GICR_MOV{LPI,ALL}R are two IMP
DEF registers and might be defined by some specific micro-architecture.

As they're not used anywhere in the kernel, just drop all of them.

Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
[maz: added context explaination]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200630134126.880-1-yuzenghui@huawei.com