usb: pd: pdphy: Update Tx Trim setting

HW recommendation is to set the TX_TRIM_3 value to 0x2 for
a steeper slope. This improves eye diagram testing result.
This register is secure access so write to the SEC_ACCESS
prior to setting this.

Change-Id: I80b0a02feb0e4d1fb382407087fa30f390641ccb
Signed-off-by: Jack Pham <jackp@codeaurora.org>