dma-mapping: consolidate the NO_DMA definition in kernel/dma/Kconfig

Have a single definition that architetures can select.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NRich Felker <dalias@libc.org>

arch/m68k/Kconfig

@@ -17,6 +17,7 @@ config M68K
 	select HAVE_COPY_THREAD_TLS
 	select GENERIC_IRQ_SHOW
 	select GENERIC_ATOMIC64
+	select NO_DMA if !MMU && !COLDFIRE
 	select HAVE_UID16
 	select VIRT_TO_BUS
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG if RMW_INSNS
@@ -60,9 +61,6 @@ config TIME_LOW_RES
 config NO_IOPORT_MAP
 	def_bool y
 
-config NO_DMA
-	def_bool (MMU && SUN3) || (!MMU && !COLDFIRE)
-
 config ZONE_DMA
 	bool
 	default y

arch/m68k/Kconfig.machine

@@ -126,6 +126,7 @@ config SUN3
 	depends on MMU
 	depends on !MMU_MOTOROLA
 	select MMU_SUN3 if MMU
+	select NO_DMA
 	select M68020
 	help
 	  This option enables support for the Sun 3 series of workstations

arch/um/Kconfig

@@ -15,6 +15,7 @@ config UML
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DEBUG_BUGVERBOSE
 	select HAVE_COPY_THREAD_TLS
+	select NO_DMA
 	select GENERIC_IRQ_SHOW
 	select GENERIC_CPU_DEVICES
 	select GENERIC_CLOCKEVENTS
@@ -168,9 +169,6 @@ config MMAPPER
 	  This driver allows a host file to be used as emulated IO memory inside
 	  UML.
 
-config NO_DMA
-	def_bool y
-
 config PGTABLE_LEVELS
 	int
 	default 3 if 3_LEVEL_PGTABLES

kernel/dma/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
 
+config NO_DMA
+	bool
+
 config HAS_DMA
 	bool
 	depends on !NO_DMA