Add support for PMC Pm25LD series

This patch adds support for
 - Pm25LD256C
 - Pm25LD512(C)
 - Pm25LD010(C)
 - Pm25LD020(C)
 - Pm25LD040(C)

These seem to be the successors of the Pm25LV series.
The main difference seems to be the dual I/O and additional erase opcodes.
Some support an additional, complex locking register (maybe all of the
above, but available datahsheets do not indicate it for all).

The Pm25LD512C was tested by Chi Zhang:
http://paste.flashrom.org/view.php?id=1579

Corresponding to flashrom svn r1671.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
diff --git a/spi25_statusreg.c b/spi25_statusreg.c
index c089157..53952fe 100644
--- a/spi25_statusreg.c
+++ b/spi25_statusreg.c
@@ -262,6 +262,7 @@
 
 /* Works for many chips of the
  * AMIC A25L series
+ * PMC Pm25LD series
  */
 int spi_prettyprint_status_register_default_bp2(struct flashctx *flash)
 {