Adapt mbuf, gpstime kernel modules to Linux 5.x in Debian bullseye

The Linux 5.10 kernel in Debian 11/bullseye has changes from the 4.19 kernel in Debian 10/buster. We need to adapt the mbuf and gpstime modules to handle it.

Known items HAVE_UNLOCKED_IOCTL removed in kernel 5.9 ioremap_nocache removed in kernel 5.6 timespec, current_kernel_time() removed in kernel 5.6 (new timekeeping routines) proc_create uses proc_ops as of kernel 5.6