arm_gic: Fix sizes of state fields in preparation for vmstate support

In preparation for switching to vmstate for migration support, fix
the sizes of various GIC state fields. In particular, we replace all
the bitfields (which VMState can't deal with) with straightforward
uint8_t values which we do bit operations on. (The bitfields made
more sense when NCPU was set differently in different situations,
but we now always model at the architectural limit of 8.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Igor Mitsyanko <i.mitsyanko@gmail.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Message-id: 1363975375-3166-3-git-send-email-peter.maydell@linaro.org
