powerpc/85xx: Protect all LBC code with CONFIG_FSL_LBC

Future SoC (like the P1010) replace the LBC controller with the new IFC
(Integrated Flash Controller) so ensure we properly protect code that is
related to the LBC.

Signed-off-by: Dipen Dudhat <Dipen.Dudhat@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>