core: ofnode: Have ofnode_read_u32_default return a u32

It was returning an int, which doesn't work if the u32 it is reading,
or the default value, will overflow a signed int.

While it could be made to work, when using a C standard/compiler where
casting negative signed values to unsigned has a defined behavior,
combined with careful casting, it seems obvious one is meant to use
ofnode_read_s32_default() with signed values.

Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: NTrent Piepho <tpiepho@impinj.com>

drivers/core/ofnode.c

@@ -39,7 +39,7 @@ int ofnode_read_u32(ofnode node, const char *propname, u32 *outp)
 	return 0;
 }
 
-int ofnode_read_u32_default(ofnode node, const char *propname, u32 def)
+u32 ofnode_read_u32_default(ofnode node, const char *propname, u32 def)
 {
 	assert(ofnode_valid(node));
 	ofnode_read_u32(node, propname, &def);

include/dm/ofnode.h

@@ -224,7 +224,7 @@ static inline int ofnode_read_s32(ofnode node, const char *propname,
  * @def:	default value to return if the property has no value
  * @return property value, or @def if not found
  */
-int ofnode_read_u32_default(ofnode ref, const char *propname, u32 def);
+u32 ofnode_read_u32_default(ofnode ref, const char *propname, u32 def);
 
 /**
  * ofnode_read_s32_default() - Read a 32-bit integer from a property