x86/irq: Add hardcoded hypervisor interrupts to /proc/stat

Some hypervisor interrupts (such as for Hyper-V VMbus and Hyper-V timers)
have hardcoded interrupt vectors on x86 and don't have Linux IRQs assigned.
These interrupts are shown in /proc/interrupts, but are not reported in
the first field of the "intr" line in /proc/stat because the x86 version
of arch_irq_stat_cpu() doesn't include them.

Fix this by adding code to arch_irq_stat_cpu() to include these interrupts,
similar to existing interrupts that don't have Linux IRQs.

Use #if IS_ENABLED() because unlike all the other nearby #ifdefs,
CONFIG_HYPERV can be built as a module.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/1677523568-50263-1-git-send-email-mikelley%40microsoft.com