kernel no longer builds without nvme

[Michael Butler]

For those of us who build "minimal" kernels:

Building /usr/obj/usr/src/sys/VM02/vers.c
Building /usr/obj/usr/src/sys/VM02/vers.o
Building /usr/obj/usr/src/sys/VM02/kernel
--- kernel ---
linking kernel
cam_xpt.o: In function `xpt_announce_periph':
/usr/src/sys/cam/cam_xpt.c:(.text+0xcd2): undefined reference to
`nvme_print_ident'
cam_xpt.o: In function `xpt_denounce_periph':
/usr/src/sys/cam/cam_xpt.c:(.text+0xe76): undefined reference to
`nvme_print_ident'
cam_xpt.o: In function `xpt_run_devq':
/usr/src/sys/cam/cam_xpt.c:(.text+0x2bc0): undefined reference to
`nvme_op_string'
/usr/src/sys/cam/cam_xpt.c:(.text+0x2bd8): undefined reference to
`nvme_cmd_string'
cam_xpt.o: In function `xpt_bus_register':
/usr/src/sys/cam/cam_xpt.c:(.text+0x620b): undefined reference to
`nvme_get_xport'
*** [kernel] Error code 1

	imb