poky: reset subtree on master HEAD(a88251b3e7)

As part of the last subtree update, I used master-next as the
subtree basis because there was a fix we needed in order to get QEMU
to pass.  I didn't realize that master-next deviated (because they use
to just have short-term patches in it).  Reset the content to the same
fix but from the master branch.

Change-Id: Ic7d2f0ac42e9da3eb263586b26ba56d8798d5bcf
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/poky/meta/lib/oe/sstatesig.py b/poky/meta/lib/oe/sstatesig.py
index 5950b3e..a46e550 100644
--- a/poky/meta/lib/oe/sstatesig.py
+++ b/poky/meta/lib/oe/sstatesig.py
@@ -431,10 +431,7 @@
                 actual_hashval = get_hashval(fullpath)
                 if actual_hashval in hashfiles:
                     continue
-                try:
-                    hashfiles[actual_hashval] = {'path':fullpath, 'sstate':True, 'time':get_time(fullpath)}
-                except FileNotFoundError:
-                    bb.warn("Could not obtain mtime for {}".format(fullpath))
+                hashfiles[actual_hashval] = {'path':fullpath, 'sstate':True, 'time':get_time(fullpath)}
 
     return hashfiles