rs9lcd: Fix segfault with unusual modes.

rs9lcd: Fix segfault with unusual modes.

Some unusual modes required re-parsing the value. Instead of assigning the
re-parsed value to *floatval, it was reassigned directly to *analog->data;
however, analog->data is not initialized at this point, causing a segfault.
This situation was created when moving the radioshack-dmm code to serial-dmm,
with the segfault not being observed at that time.

Do not write directly to analog->data, but instead use the intermediate
variable rawval.

Signed-off-by: Alexandru Gagniuc <redacted>