ld scripts: drop duplication of standard sections

Instead of every "simple" target having their own duplicate file with
all the section mappings, just provide a single, simple,
"cortex-m-generic.ld" that works with our startup code and any simple
rom/ram system.  This also drops the pointless copying of files all over
the place.  Using -L flags properly is sufficient, and the standard file
is now in the root of the library already.

lib/stm32/f1/stm32f100xe.ld

@@ -27,5 +27,5 @@ MEMORY
 }
 
 /* Include the common ld script. */
-INCLUDE libopencm3_stm32f1.ld
+INCLUDE cortex-m-generic.ld