config: Move ASHMEM into conditional (MR 2176)

Option was dropped and is no longer available.

See https://lore.kernel.org/all/20220315123457.2354812-1-hch@lst.de
And 721412ed3d

pmb/config/__init__.py

@@ -336,7 +336,6 @@ necessary_kconfig_options_anbox = {
             "SQUASHFS_XZ": True,
             "SQUASHFS_XATTR": True,
             "TMPFS_XATTR": True,
-            "ASHMEM": True,
             "ANDROID_BINDER_IPC": True,
             "ANDROID_BINDERFS": False,
             "ANDROID_BINDER_DEVICES": ["binder", "hwbinder"],
@@ -362,6 +361,11 @@ necessary_kconfig_options_anbox = {
             "PSI": True,  # required by userspace OOM killer in Waydroid
             "PSI_DEFAULT_DISABLED": False,
         }
+    },
+    "<5.18_rc1": {  # option has been dropped
+        "all": {
+            "ASHMEM": True,
+        }
     }
 }