lib/vsprintf: update comment about simple_strto<foo>() functions

lib/vsprintf: update comment about simple_strto<foo>() functions

The commit da3233d2e55f ("kernel.h: update comment about simple_strto<foo>()
functions") updated a comment regard to simple_strto<foo>() functions, but
missed similar change in the vsprintf.c module.

Update comments in vsprintf.c as well for simple_strto<foo>() functions.

Link: https://lore.kernel.org/r/20200221085723.42469-1-andriy.shevchenko@linux.intel.com
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>