Fix for CM3DS GPIO api

[kapi90]

Description

This patch aims to deploy a fix for gpio_api.c, in which the led IO writing function did not get registered properly in the GPIO structure during initialization.

@ashok-rao

Pull request type

[X] Fix
[ ] Refactor
[ ] New target
[ ] Feature
[ ] Breaking change

[cmonr]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2796
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7693/

Triggering tests

/morph test
/morph uvisor-test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2426
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7693/

[cmonr]

/morph test

[mbed-ci]

Test : SUCCESS

Build number : 2536
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7693/2536