drm/i915: use in_interrupt() not in_irq() to check context

drm/i915: use in_interrupt() not in_irq() to check context

The kernel in_irq() function tests for hard-IRQ context only, so if a
system is run with the kernel 'threadirqs' option selected, the test in
intel_check_page_flip() generates lots of warnings, because then it gets
called in soft-IRQ context.

We can instead use in_interrupt() which allows for either type of
interrupt, while still detecting and complaining about misuse of the
page flip code if it is ever called from non-interrupt context.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89321
Signed-off-by: Dave Gordon <[email protected]>
Reviewed-by: Daniel Vetter <[email protected]>
Cc: [email protected]
Signed-off-by: Jani Nikula <[email protected]>