platform: msm: gsi: Correctly allocate memory for copy_from_user

Copying from user to a global variable inside the driver is
unsafe and insecure: allocate and free the memory used for
copying from userspace in the functions doing it.

This also has the good side effect of solving a build failure
when the kernel is built with GCC >=4.9

Signed-off-by: Panchajanya1999 <panchajanya@azure-dev.live>
(cherry picked from commit ca20adfa1785903e57501145ffd4e1ff71a5a233)

Change-Id: I96d0e74fa73939883079cf2b3308dbfa7de6a453
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>