msm: cleanup: struct gsi_mhi_channel_scratch

Remove __packed from the usage of struct gsi_mhi_channel_scratch.
__packed is only needed in the struct definition and one union inclusion.

include/linux/msm_gsi.h:
struct __packed gsi_mhi_channel_scratch {
    ...
}

union __packed gsi_channel_scratch {
    ...
    struct __packed gsi_mhi_channel_scratch mhi;
    ...
}

Bug: 139442076
Bug: 139808631
Bug: 140528058
Change-Id: Ic07de9a164b88238bbe8655252b65783d846e933
Signed-off-by: Petri Gynther <pgynther@google.com>
(cherry picked from commit 43edfaab5f33aaa199f109e6c227221dbd13eac2)