drivers gpio: Fix disabling of interrupts for QMSI shims

When a GPIO pin is configured, the shim driver will first read the
current values in the controller registers to keep the other pins from
changing their configuration. After that it sets the bits for the
corresponding pin accordingly.

When the flag to enable interrupts is passed to the function, the
corresponding bits are all set properly, but no changes are made if
interrupts are not requested. This makes it impossible to disable
interrupts for a given pin once they've been enabled.

Fix it by always resetting the interrupt enabled bit when they have not
been requested. Other values can be left untouched as they won't have
any effect.

Jira: ZEP-1717

Change-Id: I30e97bb06d966291e23d0c66ddf39bce615c287b
Signed-off-by: Iván Briano <ivan.briano@intel.com>