Bluetooth: Add delay between BT enable line toggle

Add 50msec delay between BT_EN gpio line toggle from 0 to 1
during BT turn on process to allow settling time for the controller
to recongnize the BT_EN pin toggle.

Change-Id: I795ddca18ef91402c3194bedddcf30a713481a59
CRs-fixed: 690360
Signed-off-by: Pramod Kotreshappa <pramodk@codeaurora.org>