mips: mt76xx: Flush d-cache in arch_misc_init() to solve d-cache issues

It has been noticed, that sometimes the d-cache is not in a
"clean-state" when U-Boot is running on MT7688. This was detected when
using the ethernet driver (which uses d-cache) and a TFTP command does
not complete. Flushing the complete d-cache (again?) here seems to fix
this issue.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 1b1b1d7..355d3b4 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -79,7 +79,7 @@
 	select DM_SERIAL
 	imply DM_SPI
 	imply DM_SPI_FLASH
-	select ARCH_MISC_INIT if WATCHDOG
+	select ARCH_MISC_INIT
 	select MIPS_TUNE_24KC
 	select OF_CONTROL
 	select ROM_EXCEPTION_VECTORS