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/flashchips.h b/flashchips.h
index 7bcbf9e..62be293 100644
--- a/flashchips.h
+++ b/flashchips.h
@@ -450,6 +450,7 @@
 /*
  * Programmable Micro Corp is listed in JEP106W in bank 2, so it should
  * have a 0x7F continuation code prefix.
+ * Apparently this name is owned by "Chingis Technology Corporation" http://www.chingistek.com.
  */
 #define PMC_ID			0x7F9D	/* PMC */
 #define PMC_ID_NOPREFIX		0x9D	/* PMC, missing 0x7F prefix */
@@ -460,7 +461,7 @@
 #define PMC_PM25LV512		0x7B	/* Same as Pm25LV512A */
 #define PMC_PM25LV010		0x7C	/* Same as Pm25LV010A, but the former does not support RDID but RES3 only. */
 #define PMC_PM25LV020		0x7D
-#define PMC_PM25LV040		0x7E
+#define PMC_PM25LV040		0x7E	/* Same as PM25LD040(C), but the latter supports more features. */
 #define PMC_PM25LV080B		0x13
 #define PMC_PM25LV016B		0x14
 #define PMC_PM29F002T		0x1D