USB: usbtmc: use interruptible sleep in usbtmc_read

USB: usbtmc: use interruptible sleep in usbtmc_read

usbtmc_read() calls usbtmc_generic_read()
which uses interruptible sleep, but usbtmc_read()
itself uses uninterruptble sleep for mutual exclusion
between threads. That makes no sense.
Both should use interruptible sleep.

Fixes: 5b775f672cc99 ("USB: add USB test and measurement class driver")
Cc: stable <stable@kernel.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20250430134810.226015-1-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>