Add initial support for flashing some NVIDIA graphics cards

The new option is '-p gfxnvidia', rest of the interface is as usual.

I tested a successful identify and read on a "RIVA TNT2 Model 64/Model 64 Pro"
card for now, erase and write did NOT work properly so far!

Please do not attempt to write/erase cards yet, unless you can recover!

In addition to the NVIDIA handling code it was required to call
programmer_shutdown() in a lot more places, otherwise the graphics card
will be disabled in the init function, but never enabled again as the
shutdown function is not called.
The shutdown handling may be changed to use atexit() later.

Corresponding to flashrom svn r737.

Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de>
Acked-by: Luc Verhaegen <libv@skynet.be>
diff --git a/Makefile b/Makefile
index df9f73d..5cc0077 100644
--- a/Makefile
+++ b/Makefile
@@ -74,6 +74,9 @@
 # Always enable 3Com NICs for now.
 CONFIG_NIC3COM ?= yes
 
+# Always enable NVIDIA graphics cards for now.
+CONFIG_GFXNVIDIA ?= yes
+
 # Always enable SiI SATA controllers for now.
 CONFIG_SATASII ?= yes
 
@@ -107,6 +110,11 @@
 OBJS += nic3com.o
 endif
 
+ifeq ($(CONFIG_GFXNVIDIA), yes)
+FEATURE_CFLAGS += -D'GFXNVIDIA_SUPPORT=1'
+OBJS += gfxnvidia.o
+endif
+
 ifeq ($(CONFIG_SATASII), yes)
 FEATURE_CFLAGS += -D'SATASII_SUPPORT=1'
 OBJS += satasii.o