[toolchain] Do not set "soname" for loadable modules

Loadable modules declared with the loadable_module() or driver_module()
build rules are not shared libraries and should not have the SONAME
property set. It looks like this was inadvertantly copied between the
solink() and solink_module() tool definitions.

Change-Id: I597bcf09f3b87f1b454aee980f35405b4d900268
diff --git a/build/toolchain/clang_toolchain.gni b/build/toolchain/clang_toolchain.gni
index cef8c28..2524c35 100644
--- a/build/toolchain/clang_toolchain.gni
+++ b/build/toolchain/clang_toolchain.gni
@@ -403,7 +403,7 @@
         rspfile_content = "{{inputs_newline}}"
         default_output_extension = ".dylib"
       } else {
-        command = "$ld -shared {{ldflags}} -o \"$unstripped_outfile\" -Wl,--Map=\"$unstripped_outfile.map\" -Wl,-soname=\"$outname\" @\"$rspfile\" {{solibs}} {{libs}}"
+        command = "$ld -shared {{ldflags}} -o \"$unstripped_outfile\" -Wl,--Map=\"$unstripped_outfile.map\" @\"$rspfile\" {{solibs}} {{libs}}"
         rspfile_content = "{{inputs}}"
         default_output_extension = ".so"
       }