MIPS: TXx9: Fix Kconfig warnings

If TTY and SND is not n, we got this warnings:

WARNING: unmet direct dependencies detected for HAS_TXX9_SERIAL
  Depends on [n]: TTY [=n] && HAS_IOMEM [=y]
  Selected by [y]:
  - SOC_TX3927 [=y]

WARNING: unmet direct dependencies detected for HAS_TXX9_SERIAL
  Depends on [n]: TTY [=n] && HAS_IOMEM [=y]
  Selected by [y]:
  - SOC_TX4938 [=y]

Only dependencies is enabled, they can be enabled, so
use 'imply' instead of 'select' to fix this.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/txx9/Kconfig

@@ -58,7 +58,7 @@ config TOSHIBA_RBTX4939
 config SOC_TX3927
 	bool
 	select CEVT_TXX9
-	select HAS_TXX9_SERIAL
+	imply HAS_TXX9_SERIAL
 	select HAVE_PCI
 	select IRQ_TXX9
 	select GPIO_TXX9
@@ -66,30 +66,30 @@ config SOC_TX3927
 config SOC_TX4927
 	bool
 	select CEVT_TXX9
-	select HAS_TXX9_SERIAL
+	imply HAS_TXX9_SERIAL
 	select HAVE_PCI
 	select IRQ_TXX9
 	select PCI_TX4927
 	select GPIO_TXX9
-	select HAS_TXX9_ACLC
+	imply HAS_TXX9_ACLC
 
 config SOC_TX4938
 	bool
 	select CEVT_TXX9
-	select HAS_TXX9_SERIAL
+	imply HAS_TXX9_SERIAL
 	select HAVE_PCI
 	select IRQ_TXX9
 	select PCI_TX4927
 	select GPIO_TXX9
-	select HAS_TXX9_ACLC
+	imply HAS_TXX9_ACLC
 
 config SOC_TX4939
 	bool
 	select CEVT_TXX9
-	select HAS_TXX9_SERIAL
+	imply HAS_TXX9_SERIAL
 	select HAVE_PCI
 	select PCI_TX4927
-	select HAS_TXX9_ACLC
+	imply HAS_TXX9_ACLC
 
 config TXX9_7SEGLED
 	bool