arch: m68k: Add QEMU specific RAMBAR workaround

The QEMU emulation of m68k does not support RAMBAR accesses,
add Kconfig option which inhibits those accesses, so that
U-Boot can be started in m68k QEMU for CI testing purpopses
until QEMU emulation improves.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 32759cd..1911563 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -198,8 +198,17 @@
 source "board/sysam/amcore/Kconfig"
 source "board/sysam/stmark2/Kconfig"
 
+config M68K_QEMU
+	bool "Build with workarounds for incomplete QEMU emulation"
+	default n
+	help
+	  QEMU 8.x currently does not implement RAMBAR accesses and
+	  DMA timers. Enable this option for U-Boot CI purposes only
+	  to skip the RAMBAR accesses.
+
 config MCFTMR
 	bool "Use DMA timer"
-	default y
+	default y if !M68K_QEMU
+	default n if M68K_QEMU
 
 endmenu