xen/arm: Relax GIC version check

xen/arm: Relax GIC version check

Supported values are

0b0000 GIC CPU interface system registers not implemented.

0b0001 System register interface to versions 3.0 and 4.0 of the GIC
       CPU interface is supported.

0b0011 System register interface to version 4.1 of the GIC CPU
       interface is supported.

4.1 is still backward compatible with 4.0/3.0, moreover ARM ARM
guarantees that future versions of the GIC CPU interface retain
backwards compatible.

Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Acked-by: Julien Grall <jgrall@amazon.com>
Release-Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>