pcrypt: use format specifier in kobject_add

Passing string 'name' as the format specifier is potentially hazardous
because name could (although very unlikely to) have a format specifier
embedded in it causing issues when parsing the non-existent arguments
to these.  Follow best practice by using the "%s" format string for
the string 'name'.

Cleans up clang warning:
crypto/pcrypt.c:397:40: warning: format string is not a string literal
(potentially insecure) [-Wformat-security]

Fixes: a3fb1e33 ("pcrypt: Added sysfs interface to pcrypt")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>