wireless: hostap: proc: print properly escaped SSID

Instead of substituting non-printable characters by '_' let's print SSID
properly escaped by using recently added %*pE specifier.

[akpm@linux-foundation.org: fix printk type warning]
[akpm@linux-foundation.org: remove now-unused local `i']
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: "John W . Linville" <linville@tuxdriver.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>