xtensa: add missing isync to the cpu_reset TLB code

xtensa: add missing isync to the cpu_reset TLB code

BugLink: https://bugs.launchpad.net/bugs/1841652
commit cd8869f4cb257f22b89495ca40f5281e58ba359c upstream.

ITLB entry modifications must be followed by the isync instruction
before the new entries are possibly used. cpu_reset lacks one isync
between ITLB way 6 initialization and jump to the identity mapping.
Add missing isync to xtensa cpu_reset.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>