powerpc/t2080qds: remove spurious x permission from README file

It doesn't make sense for a README file to be executable. Remove that
bit.

Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>
diff --git a/board/freescale/t208xqds/README b/board/freescale/t208xqds/README
old mode 100755
new mode 100644