scripts: Makefile.lib: Sanitize DTB names

Having dashes as a separator in the DTB name is a quite common practice.

However, the current code to generate objects from DTBs assumes the
separator is an underscore, leading to a compilation error when building a
device tree with dashes.

Replace all the dashes in the DTB name to generate the symbols name, which
should solve this issue.

Acked-by: Simon Glass <sjg@chromium.org>
Acked-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

scripts/Makefile.lib

@@ -275,11 +275,11 @@ cmd_dt_S_dtb=						\
 (							\
 	echo '.section .dtb.init.rodata,"a"';		\
 	echo '.balign 16';				\
-	echo '.global __dtb_$(*F)_begin';		\
-	echo '__dtb_$(*F)_begin:';			\
+	echo '.global __dtb_$(subst -,_,$(*F))_begin';	\
+	echo '__dtb_$(subst -,_,$(*F))_begin:';		\
 	echo '.incbin "$<" ';				\
-	echo '__dtb_$(*F)_end:';			\
-	echo '.global __dtb_$(*F)_end';			\
+	echo '__dtb_$(subst -,_,$(*F))_end:';		\
+	echo '.global __dtb_$(subst -,_,$(*F))_end';	\
 	echo '.balign 16';				\
 ) > $@