The pci/htirq.c file was removed so remove it from the documentation
file also.

Error: Cannot open file ../drivers/pci/htirq.c
WARNING: kernel-doc '../scripts/kernel-doc -rst -enable-lineno -export ../drivers/pci/htirq.c' failed with return code 2

Fixes: fd2fa6c1 ("x86/PCI: Remove unused HyperTransport interrupt support")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>