usb: phy: qusb: Fix occasional glitch issue with DP/DM pulse transition

Due to having two set of registers to enable/disable pullup and pulldown
registers if DP/DM is kept into high-z state for fraction of time, there
is occasional glitch seen on falling or rising edge with DP/DM pulse. To
address this issue, take approach of "make-before-break" (i.e. enable
required pulldown or pullup before removing pullup or pulldown) which makes
sure that DP/DM pulse transition is clean.

Change-Id: Ia140561a423a4c6258d1c90e2926b2db0c4d8093
Signed-off-by: Mayank Rana <mrana@codeaurora.org>