firmware: always create dynsym section

With a bare-metal linkers (e.g. riscv64-elf-ld), there exists no
dynsym section. The dynsym section is not used by OpenSBI but
discarding it makes linkers with dynamic library support unhappy.

Signed-off-by: Leon M. Busch-George <leon@georgemail.eu>
Reviewed-by: Anup Patel <anup@brainfault.org>
diff --git a/firmware/fw_base.ldS b/firmware/fw_base.ldS
index c15ccdb..fb47984 100644
--- a/firmware/fw_base.ldS
+++ b/firmware/fw_base.ldS
@@ -38,6 +38,11 @@
 		. = ALIGN(8);
 	}
 
+	.dynsym :
+	{
+		*(.dynsym)
+	}
+
 	. = ALIGN(0x1000); /* Ensure next section is page aligned */
 
 	.rela.dyn : {