[ARM] 3971/1: xsc3: get rid of L_PTE_COHERENT

Merge L_PTE_COHERENT with L_PTE_SHARED and free up a L_PTE_* bit.

Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>