[MIPS] Drop unneeded config options for RBTX4938

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 4b02d8a..e7d542d 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -558,9 +558,7 @@
 
 config TOSHIBA_RBTX4938
 	bool "Toshiba RBTX4938 board"
-	select HAVE_STD_PC_SERIAL_PORT
 	select DMA_NONCOHERENT
-	select GENERIC_ISA_DMA
 	select HAS_TXX9_SERIAL
 	select HW_HAS_PCI
 	select IRQ_CPU