Buffer-too-small check for device TCTI doesn't work

[zanebeckwith]

The check in tss2_tcti_device.c for a too-small buffer, using EOF return from read, doesn't work, as determined by tss2_tdcti_device-test.c.

I think the driver always returns whatever it can (either everything, or just what can fit in the buffer), then always closes the fd. So, this will always return EOF, so this check doesn't work.