s390/hmcdrv: Restrict s390 HMC driver to S390 arch

This driver is only usable on 64-bit s390 machines.  Mark the Kconfig
dependencies to that users on other architectures are not prompted for it.

Fixes: 8f933b1043e1e5 ("s390/hmcdrv: HMC drive CD/DVD access")
Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/char/Kconfig

@@ -105,7 +105,7 @@ config SCLP_ASYNC
 config HMC_DRV
 	def_tristate m
 	prompt "Support for file transfers from HMC drive CD/DVD-ROM"
-	depends on 64BIT
+	depends on S390 && 64BIT
 	select CRC16
 	help
 	  This option enables support for file transfers from a Hardware