psm: Add a kludge to support 0x46 identity middle byte Synaptics touchpads

Most synaptics touchpads return 0x47 in middle byte in responce to identify
command as stated in p.4.4 of "Synaptics PS/2 TouchPad Interfacing Guide".
But some devices e.g. found on HP EliteBook 9470m return 0x46 here.
Allow them to be identified as Synaptics as well as 0x47.
ExtendedQueries return incorrect data on such a touchpads so we ignore
their result and set conservative defaults.

PR: 222667
Reported by: Neel Chauhan <neel@neelc.org>
Tested by: Neel Chauhan <neel@neelc.org>
Approved by: gonzo