Input: serio-raw - fix potential serio port name truncation

Input: serio-raw - fix potential serio port name truncation

When compiling with W=1 the following warnings are triggered:

drivers/input/serio/serio_raw.c: In function ‘serio_raw_connect’:
drivers/input/serio/serio_raw.c:303:28: error: ‘%ld’ directive output may be truncated writing between 1 and 11 bytes into a region of size 7 [-Werror=format-truncation=]
  303 |                  "serio_raw%ld", (long)atomic_inc_return(&serio_raw_no));

atomic_inc_return() returns an int, so there is no reason to cast it
to long and print as such. Fix the issue by removing the cast,
printing it as unsigned decimal, and expanding the name from 16 to 20
bytes to accommodate the largest possible port number.

Link: https://lore.kernel.org/r/20240905041732.2034348-22-dmitry.torokhov@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>