msm: cleanup: union gsi_channel_scratch

Remove __packed from the usage of union gsi_channel_scratch.
__packed is only needed in the union definition.

include/linux/msm_gsi.h:
union __packed gsi_channel_scratch {
    ...
}

Bug: 139442076
Bug: 139808631
Change-Id: If59d3d217e6a4bae92b9931523e2f89a39a04be9
Signed-off-by: Petri Gynther <pgynther@google.com>