fsi: aspeed: add unspecified HAS_IOMEM dependency

Currently CONFIG_FSI_MASTER_ASPEED=y implicitly depends on
CONFIG_HAS_IOMEM=y; consequently, on architectures without IOMEM we get
the following build error:

ld: drivers/fsi/fsi-master-aspeed.o: in function `fsi_master_aspeed_probe':
drivers/fsi/fsi-master-aspeed.c:436: undefined reference to `devm_ioremap_resource'

Fix the build error by adding the unspecified dependency.

Fixes: 606397d6 ("fsi: Add ast2600 master driver")
Cc: stable@vger.kernel.org
Reported-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20200131034832.294268-1-joel@jms.id.auSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/fsi/Kconfig

@@ -55,6 +55,7 @@ config FSI_MASTER_AST_CF
 
 config FSI_MASTER_ASPEED
 	tristate "FSI ASPEED master"
+	depends on HAS_IOMEM
 	help
 	 This option enables a FSI master that is present behind an OPB bridge
 	 in the AST2600.