Revert "alpha-softmmu: Disable for the 0.15 release branch."

This reverts commit 46f08792bb4a69ab8aab897c174d82b006026140.

This was not supposed to be applied to mainline.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
diff --git a/configure b/configure
index ad924c4..414317a 100755
--- a/configure
+++ b/configure
@@ -855,6 +855,7 @@
     default_target_list="\
 i386-softmmu \
 x86_64-softmmu \
+alpha-softmmu \
 arm-softmmu \
 cris-softmmu \
 lm32-softmmu \