lguest: fix crash lguest_time_init

fe25c7fc "x86: lguest: Convert to new irq chip functions" converted
enable_lguest_irq() to take a struct irq_data *, but didn't fix the one
internal caller.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
To: x86@kernel.org