mfd: timberdale: Remove redundant assignment to variable err

mfd: timberdale: Remove redundant assignment to variable err

The variable err is being assigned -ENODEV and then err is being
re-assigned the same error value via the error exit label err_mfd.
The assignment is redundant and can be removed.

Cleans up clang scan build warning:
drivers/mfd/timberdale.c:768:3: warning: Value stored to 'err' is
never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20240415102632.484411-1-colin.i.king@gmail.com
Signed-off-by: Lee Jones <lee@kernel.org>