sprintf.h requires stdarg.h

In file included from drivers/crypto/intel/qat/qat_common/adf_pm_dbgfs_utils.c:4:
include/linux/sprintf.h:11:54: error: unknown type name 'va_list'
   11 | __printf(2, 0) int vsprintf(char *buf, const char *, va_list);
      |                                                      ^~~~~~~
include/linux/sprintf.h:1:1: note: 'va_list' is defined in header '<stdarg.h>'; this is probably fixable by adding '#include <stdarg.h>'

Link: https://lkml.kernel.org/r/20250721173754.42865913@canb.auug.org.au
Fixes: 39ced19 ("lib/vsprintf: split out sprintf() and friends")
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Andriy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: sfrothwell

include/linux/sprintf.h

@@ -4,6 +4,7 @@
 
 #include <linux/compiler_attributes.h>
 #include <linux/types.h>
+#include <linux/stdarg.h>
 
 int num_to_str(char *buf, int size, unsigned long long num, unsigned int width);