vfio-pci: Break up vfio_pci_core_ioctl() into one function per ioctl

vfio-pci: Break up vfio_pci_core_ioctl() into one function per ioctl

500 lines is a bit long for a single function, move the bodies of each
ioctl into separate functions and leave behind a switch statement to
dispatch them. This patch just adds the function declarations and does not
fix the indenting. The next patch will restore the indenting.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/2-v2-0f9e632d54fb+d6-vfio_ioctl_split_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>