mb/asrock/h81m-hds: Allow "keep state" for power_on_after_fail

When I added the cmos.layout file, I did not realise that the
southbridge code cleverly emulated the "keep state" option.

Tested on an ASRock H81M-HDS. The `Keep` option works as it should.

Change-Id: I908e59d1e1eedefa6610e7f980afc3c04390a519
Signed-off-by: Tristan Corrick <tristan@corrick.kiwi>
Reviewed-on: https://review.coreboot.org/c/30102
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/mainboard/asrock/h81m-hds/cmos.layout

@@ -55,7 +55,7 @@ entries
 
 # coreboot config options: southbridge
 408          1       e       1        nmi
-409          2       e       1        power_on_after_fail
+409          2       e       5        power_on_after_fail
 
 # coreboot config options: check sums
 984          16      h       0        check_sum
@@ -84,6 +84,10 @@ enumerations
 4     7     Debug
 4     8     Spew
 
+5     0     Disable
+5     1     Enable
+5     2     Keep
+
 # -----------------------------------------------------------------
 checksums