ARM: ensure C page table setup code follows assembly code (part II)

This does the same as the previous commit, but for the S bit, which also
needs to match the initial value which the assembly code used for the
same reasons.  Again, we add a check for SMP to ensure that the page
tables are correctly setup for SMP.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>