s390/pkey: Fix checkpatch findings in pkey header file
Fix all the complains from checkpatch for the pkey header file:
CHECK: No space is necessary after a cast
+ PKEY_TYPE_CCA_DATA = (__u32) 1,
CHECK: Please use a blank line after function/struct/union/enum declarations
+};
+#define PKEY_GENSECK _IOWR(PKEY_IOCTL_MAGIC, 0x01, struct pkey_genseck)