vsprintf: remove redundant and unused %pCn format specifier

vsprintf: remove redundant and unused %pCn format specifier

%pC and %pCn print the same string, and commit 900cca294425 ("lib/vsprintf:
add %pC{,n,r} format specifiers for clocks") introducing them does not
clarify any intended difference. It can be assumed %pC is a default for
%pCn as some other specifiers do, but not all are consistent with this
policy. Moreover there is now no other suffix other than 'n', which makes a
default not really useful.

All users in the kernel were using %pC except for one which has been
converted. So now remove %pCn and all the unnecessary extra code and
documentation.

Acked-by: Stephen Boyd <sboyd@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Yanteng Si <si.yanteng@linux.dev>
Link: https://lore.kernel.org/r/20250311-vsprintf-pcn-v2-2-0af40fc7dee4@bootlin.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>