Currently we split each config line on the equals sign, assuming that
there's only one equals sign there.  This isn't a valid assumption for
cases like:

    CONFIG_CMDLINE="console=ttyAMA0"

Fix this by splitting at the first equals sign, rather than splitting
at *all* equals signs.

Change-Id: I01e44fe2e9a0f09a8bebdd76715002f6b12cf0b5