board_info.txt: Categorize various boards

Info supplied by: idwer

Change-Id: I3086e8118a721ded33c578c6c82e20642ef9d776
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/4733
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Tested-by: build bot (Jenkins)

src/mainboard/amd/serengeti_cheetah_fam10/board_info.txt

@@ -0,0 +1 @@
+Category: server

src/mainboard/roda/rk9/board_info.txt

@@ -0,0 +1 @@
+Category: laptop

src/mainboard/supermicro/h8dmr_fam10/board_info.txt

@@ -0,0 +1 @@
+Category: server

src/mainboard/supermicro/h8scm_fam10/board_info.txt

@@ -0,0 +1 @@
+Category: server

src/mainboard/tyan/s2912_fam10/board_info.txt

@@ -0,0 +1 @@
+Category: server

src/mainboard/tyan/s8226/board_info.txt

@@ -0,0 +1 @@
+Category: server