Convert CONFIG_FLASH_SHOW_PROGRESS to Kconfig

This converts the following to Kconfig:
   CONFIG_FLASH_SHOW_PROGRESS

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/boston64r2_defconfig b/configs/boston64r2_defconfig
index 253d232..8003166 100644
--- a/configs/boston64r2_defconfig
+++ b/configs/boston64r2_defconfig
@@ -43,6 +43,7 @@
 CONFIG_MTD=y
 CONFIG_DM_MTD=y
 CONFIG_MTD_NOR_FLASH=y
+CONFIG_FLASH_SHOW_PROGRESS=0
 CONFIG_CFI_FLASH=y
 CONFIG_SYS_FLASH_USE_BUFFER_WRITE=y
 CONFIG_SYS_FLASH_PROTECTION=y