xen/pt: Avoid NULL dereference in hvm_pirq_eoi()

xen/pt: Avoid NULL dereference in hvm_pirq_eoi()

Coverity warns that pirq_dpci unconditionally dereferences a NULL pointer.
This warning appears to be triggered by pirq_dpci() which is a hidden ternary
expression.  In reality, it appears that both callers pass a non-NULL pirq
parameter, so the code is ok in practice.

Rearange the logic to fail-safe, which should quiesce Coverity.

Clean up bool_t => bool and trailing whitespace for hvm_domain_use_pirq()
while auditing this area.

No (intended) functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>