Add RAM3 support for L4-Plus to linker generation

This only adds basic support.
Specific settings still need to be added.

ld/linker.ld.S

@@ -47,6 +47,9 @@ MEMORY
 #if defined(_RAM2)
 	ram2 (rwx) : ORIGIN = _RAM2_OFF, LENGTH = _RAM2
 #endif
+#if defined(_RAM3)
+	ram3 (rwx) : ORIGIN = _RAM3_OFF, LENGTH = _RAM3
+#endif
 #if defined(_CCM)
 	ccm (rwx) : ORIGIN = _CCM_OFF, LENGTH = _CCM
 #endif
@@ -151,6 +154,13 @@ SECTIONS
 	} >ram2
 #endif
 
+#if defined(_RAM3)
+	.ram3 : {
+		*(.ram3*)
+		. = ALIGN(4);
+	} >ram3
+#endif
+
 #if defined(_XSRAM)
 	.xsram : {
 		*(.xsram*)