board-msm7x27a: correct virtual key assignment for u8815

As far as I can tell, u8815 is the only device that is incorrect here.

Original change by Fagulhas: https://github.com/Fagulhas/android_kernel_huawei_msm7x27a/commit/59cc6f198802ad3d0ff2a6fe42b58007a4b960c3