binman: Update elf to return number of written symbols

Update the LookupAndWriteSymbols() function to return the number of
symbols written. Also add some logging for when debugging is not
enabled.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/elf_test.py b/tools/binman/elf_test.py
index c980839..2fb3f6f 100644
--- a/tools/binman/elf_test.py
+++ b/tools/binman/elf_test.py
@@ -141,7 +141,8 @@
         entry = FakeEntry(10)
         section = FakeSection()
         elf_fname = self.ElfTestFile('u_boot_binman_syms_bad')
-        elf.LookupAndWriteSymbols(elf_fname, entry, section)
+        count = elf.LookupAndWriteSymbols(elf_fname, entry, section)
+        self.assertEqual(0, count)
 
     def testBadSymbolSize(self):
         """Test that an attempt to use an 8-bit symbol are detected
@@ -162,7 +163,7 @@
     def testNoValue(self):
         """Test the case where we have no value for the symbol
 
-        This should produce -1 values for all thress symbols, taking up the
+        This should produce -1 values for all three symbols, taking up the
         first 16 bytes of the image.
         """
         if not elf.ELF_TOOLS:
@@ -170,7 +171,8 @@
         entry = FakeEntry(28)
         section = FakeSection(sym_value=None)
         elf_fname = self.ElfTestFile('u_boot_binman_syms')
-        elf.LookupAndWriteSymbols(elf_fname, entry, section)
+        count = elf.LookupAndWriteSymbols(elf_fname, entry, section)
+        self.assertEqual(5, count)
         expected = (struct.pack('<L', elf.BINMAN_SYM_MAGIC_VALUE) +
                     tools.get_bytes(255, 20) +
                     tools.get_bytes(ord('a'), 4))