tsnep: Fix tsnep_request_irq() format-overflow warning

tsnep: Fix tsnep_request_irq() format-overflow warning

Compiler warns about a possible format-overflow in tsnep_request_irq():
drivers/net/ethernet/engleder/tsnep_main.c:884:55: warning: 'sprintf' may write a terminating nul past the end of the destination [-Wformat-overflow=]
                         sprintf(queue->name, "%s-rx-%d", name,
                                                       ^
drivers/net/ethernet/engleder/tsnep_main.c:881:55: warning: 'sprintf' may write a terminating nul past the end of the destination [-Wformat-overflow=]
                         sprintf(queue->name, "%s-tx-%d", name,
                                                       ^
drivers/net/ethernet/engleder/tsnep_main.c:878:49: warning: '-txrx-' directive writing 6 bytes into a region of size between 5 and 25 [-Wformat-overflow=]
                         sprintf(queue->name, "%s-txrx-%d", name,
                                                 ^~~~~~

Actually overflow cannot happen. Name is limited to IFNAMSIZ, because
netdev_name() is called during ndo_open(). queue_index is single char,
because less than 10 queues are supported.

Fix warning with snprintf(). Additionally increase buffer to 32 bytes,
because those 7 additional bytes were unused anyway.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202310182028.vmDthIUa-lkp@intel.com/
Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20231023183856.58373-1-gerhard@engleder-embedded.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>