usb: ehci-msm2: Fix LOW Speed device enumeration issue

Disable ULPI_TX_PKT_EN_CLR_FIX which is valid only for HSIC core.
It otherwise causes enumeration failures with low speed devices.

Change-Id: I13e750e9b5a589aca61a06c36f66d1075e863801
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Chandra Devireddy <cdevired@codeaurora.org>