USB: cp2101: Add identifiers for the Telegesys ETRX2USB

This patch adds support for the Telegesys ETRX2USB which
works fine with the cp2101 driver.

Signed-off-by: Florian Fainelli <florian.fainelli@telecomint.eu>
Tested-by: Xavier Carcelle <xavier.carcelle@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>