staging: gpib: change return type of t1_delay function to report errors

staging: gpib: change return type of t1_delay function to report errors

The current code returns "unsigned int" and it doesn't handle errors
correctly if it happens during ioctl call for t1 delay configuration.

The ni_usb_t1_delay(), from NI, is the only function returning -1
at this point. The caller, t1_delay_ioctl(), doesn't check for errors
and sets board->t1_nano_sec to -1 and returns success.
The board->t1_nano_sec value is also used in ni_usb_setup_t1_delay()
besides the ioctl call and a value of -1 is treated as being above 1100ns.
It may or may not have a noticeable effect, but it's obviously not right
considering the content of ni_usb_setup_t1_delay().

Typical delays are in the 200-2000 range, but definitely not more
than INT_MAX so we can fix this code by changing the return type to int
and adding a check for errors. While we're at it, lets change the error
code in ni_usb_t1_delay() from -1 and instead propagate the error from
ni_usb_write_registers().

Fixes: 4e127de14fa7 ("staging: gpib: Add National Instruments USB GPIB driver")
Signed-off-by: Rodrigo Gobbi <rodrigo.gobbi.7@gmail.com>
Link: https://lore.kernel.org/r/20250225014811.77995-1-rodrigo.gobbi.7@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>