sh: place board lowlevel_init code in the beginning of .text

Reference lowlevel_init of all supported SH2A/SH3/SH4/SH4A boards
from a shared linker script, the lowlevel_init function will be called
by a relative address.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/board/espt/Makefile b/board/espt/Makefile
index 8a8a2c9..f24e9cf 100644
--- a/board/espt/Makefile
+++ b/board/espt/Makefile
@@ -8,4 +8,4 @@
 #
 
 obj-y	:= espt.o
-obj-y	+= lowlevel_init.o
+extra-y	+= lowlevel_init.o