src/mainboard/*/*/board_info.txt: Added Release year for boards

To simplify browsing the "Supported hardware" list, I added Release year
for the hardware from asus, asrock, gigabyte, msi, via, tyan, intel,
lenovo, apple, jetway and hp. Still several models and manufacturers to
add information to. This is more of a proof-of-concept.
The "Release year" will be shown in the wiki page.

Change-Id: I6bc14ed06ac7c6b3c9f054b49f08cb9b3dc47947
Signed-off-by: Mathias Friman <mathias@workplays.se>
Reviewed-on: http://review.coreboot.org/9963
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Edward O'Callaghan <edward.ocallaghan@koparo.com>

src/mainboard/gigabyte/ga-6bxc/board_info.txt

@@ -4,3 +4,4 @@ ROM package: DIP32
 ROM protocol: Parallel
 ROM socketed: y
 Flashrom support: y
+Release year: 1998

src/mainboard/gigabyte/ga-6bxe/board_info.txt

@@ -4,3 +4,4 @@ ROM package: DIP32
 ROM protocol: Parallel
 ROM socketed: y
 Flashrom support: y
+Release year: 1999

src/mainboard/gigabyte/ga-b75m-d3h/board_info.txt

@@ -4,3 +4,4 @@ ROM package: SOIC-8
 ROM protocol: SPI
 ROM socketed: n
 Flashrom support: y
+Release year: 2012

src/mainboard/gigabyte/ga-b75m-d3v/board_info.txt

@@ -4,3 +4,4 @@ ROM package: SOIC-8
 ROM protocol: SPI
 ROM socketed: n
 Flashrom support: y
+Release date: 2012

src/mainboard/gigabyte/ga_2761gxdk/board_info.txt

@@ -1,3 +1,4 @@
 Board name: GA-2761GXDK (Churchill)
 Category: desktop
 Board URL: http://www.computerbase.de/news/hardware/mainboards/amd-systeme/2007/mai/gigabyte_dtx-mainboard/
+Release year: 2007

src/mainboard/gigabyte/m57sli/board_info.txt

@@ -4,3 +4,4 @@ ROM socketed: n
 Flashrom support: y
 Vendor cooperation score: 3
 Vendor cooperation page: Gigabyte m57sli Vendor Cooperation Score
+Release year: 2006

src/mainboard/gigabyte/ma785gm/board_info.txt

@@ -1,2 +1,3 @@
 Category: desktop
 Board URL: http://www.gigabyte.us/products/product-page.aspx?pid=3447#sp
+Release year: 2009

src/mainboard/gigabyte/ma785gmt/board_info.txt

@@ -1,2 +1,3 @@
 Category: desktop
 Board URL: http://www.gigabyte.com/products/product-page.aspx?pid=3156#ov
+Release year: 2009

src/mainboard/gigabyte/ma78gm/board_info.txt

@@ -1,2 +1,3 @@
 Category: desktop
 Board URL: http://www.gigabyte.com/products/product-page.aspx?pid=2995#ov
+Release year: 2008