Kconfig: Migrate CONFIG_BAUDRATE

Move this in to Kconfig with a default of 115200.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
[trini: Run moveconfig.py, reword commit slightly]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/bf537-minotaur_defconfig b/configs/bf537-minotaur_defconfig
index fea8c32..8a6fb15 100644
--- a/configs/bf537-minotaur_defconfig
+++ b/configs/bf537-minotaur_defconfig
@@ -13,3 +13,4 @@
 CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_STMICRO=y
+CONFIG_BAUDRATE=57600