bus: bt1-axi: Build the driver into the kernel

Alas the method trigger_all_cpu_backtrace() isn't exported by the
kernel, but we need to have it called in case of the bus errors detected
to get a better description of a possible cause of the error. Let's
disable the ability to build the driver as a loadable kernel module then.
Note In future the driver will support the AXI-bus interconnect capability,
so we'd have to make it built into the kernel anyway.

Link: https://lore.kernel.org/r/20200528193113.17372-2-Sergey.Semin@baikalelectronics.ruSigned-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Olof Johansson <olof@lixom.net>
Cc: soc@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/bus/Kconfig

@@ -45,7 +45,7 @@ config BT1_APB
 	  accessed via corresponding sysfs nodes.
 
 config BT1_AXI
-	tristate "Baikal-T1 AXI-bus driver"
+	bool "Baikal-T1 AXI-bus driver"
 	depends on MIPS_BAIKAL_T1 || COMPILE_TEST
 	select MFD_SYSCON
 	help