configure: rename QEMU_GA_MSI_ENABLED to CONFIG_QGA_MSI

The QEMU_GA_MSI_ENABLED config-host.mak variable is emitted by
./configure. meson.build actually checks for CONFIG_QGA_MSI_ENABLED:

  summary_info += {'QGA MSI support':   config_host.has_key('CONFIG_QGA_MSI_ENABLED')}

Rename QEMU_GA_MSI_ENABLED to CONFIG_QGA_MSI for consistency with
CONFIG_QGA_VSS. Also use 'y' instead of 'yes' for consistency.

This fixes the feature summary printed by meson.build.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200914095231.621068-4-stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/meson.build b/meson.build
index 9755be7..975a187 100644
--- a/meson.build
+++ b/meson.build
@@ -1412,7 +1412,7 @@
   endif
   summary_info += {'QGA VSS support':   config_host.has_key('CONFIG_QGA_VSS')}
   summary_info += {'QGA w32 disk info': config_host.has_key('CONFIG_QGA_NTDDSCSI')}
-  summary_info += {'QGA MSI support':   config_host.has_key('CONFIG_QGA_MSI_ENABLED')}
+  summary_info += {'QGA MSI support':   config_host.has_key('CONFIG_QGA_MSI')}
 endif
 summary_info += {'seccomp support':   config_host.has_key('CONFIG_SECCOMP')}
 summary_info += {'coroutine backend': config_host['CONFIG_COROUTINE_BACKEND']}