drivers/i2c: ite: Add handling for read operation with 0-byte length

The current I2C driver assumes that at least one byte will be read in CQ
(command queue) mode. However, when a 0-byte read is issued
(e.g., by cmd_i2c_scan),
The read handler uses (len - 1) to set the command queue length.
When len is 0, this underflows to 0xFF, leading to an incorrect transfer
length and possible crash.

To fix this, add a check in cq_mode_allowed() for reads with length 0:

-Fallback to PIO mode in such cases.
-Properly handle 0-byte reads by issuing STOP (E_FINISH) when the slave
 address is acknowledged.
-Add appropriate handling for NACK conditions when the slave address is
 not acknowledged.

Signed-off-by: Tim Lin <tim2.lin@ite.corp-partner.google.com>