drivers/misc/pti.c: add missing includes

Found on allmodconfig build (ARCH=alpha)

    drivers/misc/pti.c: In function 'get_id':
    drivers/misc/pti.c:249: error: implicit declaration of function 'kmalloc'
    drivers/misc/pti.c: In function 'pti_char_write':
    drivers/misc/pti.c:658: error: implicit declaration of function 'copy_from_user'

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: J Freyensee <james_p_freyensee@linux.intel.com>
Cc: Jeremy Rocher <rocher.jeremy@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>