alpha: switch boards to "default y"

Some targets use "default y" for boards to filter out those that require
TCG.  For consistency we are switching all other targets to do the same.
Start with Alpha.

No changes to generated config-devices.mak file.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

.gitlab-ci.d/buildtest.yml

@@ -661,7 +661,7 @@ build-without-defaults:
       --disable-pie
       --disable-qom-cast-debug
       --disable-strip
-    TARGETS: avr-softmmu s390x-softmmu sh4-softmmu
+    TARGETS: alpha-softmmu avr-softmmu s390x-softmmu sh4-softmmu
       sparc64-softmmu hexagon-linux-user i386-linux-user s390x-linux-user
     MAKE_CHECK_ARGS: check
 

configs/devices/alpha-softmmu/default.mak

@@ -5,6 +5,5 @@
 #CONFIG_PCI_DEVICES=n
 #CONFIG_TEST_DEVICES=n
 
-# Boards:
-#
-CONFIG_DP264=y
+# Boards are selected by default, uncomment to keep out of the build.
+# CONFIG_DP264=n

hw/alpha/Kconfig

@@ -1,5 +1,7 @@
 config DP264
     bool
+    default y
+    depends on ALPHA
     imply PCI_DEVICES
     imply TEST_DEVICES
     imply E1000_PCI