configs: Enable THUMB2 on various ARM boards

The clearfog, corvus, wb45n and picosam9g45 configs are close to
exceeding their size limits, so enable THUMB2 builds on them to reclaim
space.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/wb45n_defconfig b/configs/wb45n_defconfig
index 33591d7..9d881e5 100644
--- a/configs/wb45n_defconfig
+++ b/configs/wb45n_defconfig
@@ -1,4 +1,5 @@
 CONFIG_ARM=y
+CONFIG_SYS_THUMB_BUILD=y
 CONFIG_ARCH_AT91=y
 CONFIG_SYS_TEXT_BASE=0x23f00000
 CONFIG_TARGET_WB45N=y