x86/hpet: Refactor code using deprecated strncpy() interface to use strscpy()

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

A suitable replacement is `strscpy` [2] due to the fact that it
guarantees NUL-termination on its destination buffer argument which is
_not_ the case for `strncpy`!

In this case, it is a simple swap from `strncpy` to `strscpy`. There is
one slight difference, though. If NUL-padding is a functional
requirement here we should opt for `strscpy_pad`. It seems like this
shouldn't be needed as I see no obvious signs of any padding being
required.

Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: KSPP#90
Link: https://lore.kernel.org/r/20230822-strncpy-arch-x86-kernel-hpet-v1-1-2c7d3be86f4a@google.com

Author: JustinStitt

arch/x86/kernel/hpet.c

@@ -421,7 +421,7 @@ static void __init hpet_legacy_clockevent_register(struct hpet_channel *hc)
 	 * the IO_APIC has been initialized.
 	 */
 	hc->cpu = boot_cpu_data.cpu_index;
-	strncpy(hc->name, "hpet", sizeof(hc->name));
+	strscpy(hc->name, "hpet", sizeof(hc->name));
 	hpet_init_clockevent(hc, 50);
 
 	hc->evt.tick_resume	= hpet_clkevt_legacy_resume;