speakup: only build serialio when ISA is enabled

Drivers using serialio were already made available in Kconfig only under
the ISA condition.
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20200804160659.7y76sdseow43lfms@functionSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/accessibility/speakup/Kconfig

@@ -42,6 +42,11 @@ config SPEAKUP
 		one of the listed synthesizers, you should say n.
 
 if SPEAKUP
+
+config SPEAKUP_SERIALIO
+	def_bool y
+	depends on ISA || COMPILE_TEST
+
 config SPEAKUP_SYNTH_ACNTSA
 	tristate "Accent SA synthesizer support"
 	help
@@ -52,7 +57,7 @@ config SPEAKUP_SYNTH_ACNTSA
 
 config SPEAKUP_SYNTH_ACNTPC
 	tristate "Accent PC synthesizer support"
-	depends on ISA || COMPILE_TEST
+	depends on SPEAKUP_SERIALIO
 	help
 		This is the Speakup driver for the accent pc
 		synthesizer.  You can say y to build it into the kernel,
@@ -104,7 +109,7 @@ config SPEAKUP_SYNTH_DECEXT
 
 config SPEAKUP_SYNTH_DECPC
 	depends on m
-	depends on ISA || COMPILE_TEST
+	depends on SPEAKUP_SERIALIO
 	tristate "DECtalk PC (big ISA card) synthesizer support"
 	help
 
@@ -127,7 +132,7 @@ config SPEAKUP_SYNTH_DECPC
 
 config SPEAKUP_SYNTH_DTLK
 	tristate "DoubleTalk PC synthesizer support"
-	depends on ISA || COMPILE_TEST
+	depends on SPEAKUP_SERIALIO
 	help
 
 		This is the Speakup driver for the internal DoubleTalk
@@ -138,7 +143,7 @@ config SPEAKUP_SYNTH_DTLK
 
 config SPEAKUP_SYNTH_KEYPC
 	tristate "Keynote Gold PC synthesizer support"
-	depends on ISA || COMPILE_TEST
+	depends on SPEAKUP_SERIALIO
 	help
 
 		This is the Speakup driver for the Keynote Gold

drivers/accessibility/speakup/Makefile

@@ -25,8 +25,8 @@ speakup-y := \
 	keyhelp.o \
 	kobjects.o \
 	selection.o \
-	serialio.o \
 	spk_ttyio.o \
 	synth.o \
 	thread.o \
 	varhandlers.o
+speakup-$(CONFIG_SPEAKUP_SERIALIO) += serialio.o