staging: gpib: Change return type and error code of fluke_get_dma_residue

staging: gpib: Change return type and error code of fluke_get_dma_residue

fluke_get_dma_residue() returns unsigned int with -1 as error code.
This error cannot be caught.
Fix this by changing the return type of the function to int and
returning the error code, that was captured. Also, change the data
type of variable residue to int in the function fluke_dma_read().

Fixes: 55936779f496 ("staging: gpib: Add Fluke cda based cards GPIB driver")
Signed-off-by: Everest K.C. <everestkc@everestkc.com.np>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20241017092511.17621-1-everestkc@everestkc.com.np
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>