Since the grep would fail for most devices and the result wasn't
checked, the script would exit on the first device ID that didn't match.
Also initialize $rootdir so ioat_pci.h can be located.
Change-Id: I6a714772e22692ab002e1971134d2a86edc81d92
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>