xen/arm: domain_vgic_init: Avoid double free on shared_irqs

When the function domain_vgic_init is failing to initialize pending_irqs,
it will free shared_irqs. Few call later, domain_vgic_free will be called
an try to free a second time the same variable. This will result to a double
free.

Remove the free in domain_vgic_init and rely on domain_vgic_free to correctly
release the memory.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
(cherry picked from commit 7b41618f5a08145b0198af4a8a2ce361d7e677e6)
call vgic_en/disable_irqs holding the rank_lock

Modifying ienable and calling vgic_enable_irqs or vgic_disable_irqs need
to be atomic. Move the calls to vgic_enable_irqs and vgic_disable_irqs
before releasing the rank lock.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

[ ijc -- partial backport of just the locking part of 5b3a817ea33b
         "xen/arm: observe itargets setting in vgic_enable_irqs and
         vgic_disable_irqs"
]