staging: comedi: adl_pci6208: remove redundant initialization of 'val'

Variable 'val' is initialized with a value that is never read, it is
updated with a new value again after intitialization. Remove the
redundant initialization and move the declaration and assignment into
the scope of the for-loop.

Cleans up clang warning:
drivers/staging/comedi/drivers/adl_pci6208.c:61:15: warning: Value
stored to 'val' during its initialization is never read

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>