devfreq: spdm: Fix bad pointer access

If the spdm governor fails to connect to the hypervisor correctly
the device it is supposed to be governing will be freed but still
stored in the local list.  This patch removes the device from the
list to prevent accessing an invalid pointer if the hypervisor returns
an error.

Change-Id: I536c198b5a25adbd3044ffd37d9951c197b1dfd9
Signed-off-by: Dan Sneddon <dsneddon@codeaurora.org>