Documentation: dt: keystone: Fix up missing quotes

Add missing commits for the suggest compatible flags in dt binding.

Fixes: 8841cbf666d6 ("Documentation: dt: keystone: provide SoC specific compatible flags")
Reported-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>