input: touchscreen: bu21150: balance IRQ disable

IRQ enablement in driver is transferred to userspace software. Do
the same for disablement in order to avoid any IRQ unbalance issue.

Change-Id: Iba15a856b6374a8d76f5478aca7ed12d19a54fe1
Signed-off-by: Chun Zhang <chunz@codeaurora.org>
Signed-off-by: Bharat Pawar <bpawar@codeaurora.org>
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>