input: touchscreen: add delay after enabling regulators

ITE tech touch controller needs a delay to come to an active
state after regulators are enabled and do any i2c transactions.
So this change adds a delay for the same.

Change-Id: Ifd7c936d8f5d364b78c64aeebd1517d49a5b8936
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>