arm64: errata: Provide macro for major and minor cpu revisions

arm64: errata: Provide macro for major and minor cpu revisions

commit fa5ce3d1928c441c3d241c34a00c07c8f5880b1a upstream

Definition of cpu ranges are hard to read if the cpu variant is not
zero. Provide MIDR_CPU_VAR_REV() macro to describe the full hardware
revision of a cpu including variant and (minor) revision.

Signed-off-by: Robert Richter <rrichter@cavium.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
[ morse: some parts of this patch were already backported as part of
  b8c320884eff003581ee61c5970a2e83f513eff1 ]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>