staging: comedi: me_daq: replace 'result' and 'error' with 'ret'

Two local variables are used in me_attach_pci() to check for errors
when calling other functions, 'result' and 'error'. Remove both of
them and just use a common 'ret' variable.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>