alpha: replace sprintf()/strcpy() with scnprintf()/strscpy()

Replace sprintf() with the safer variant scnprintf() and use its return
value instead of calculating the string length again using strlen().

Use strscpy() instead of the deprecated strcpy().

No functional changes intended.

Link: https://github.com/KSPP/linux/issues/88
Link: https://lkml.kernel.org/r/20250521121840.5653-1-thorsten.blum@linux.dev


Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: guoweikang <guoweikang.kernel@gmail.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>