ARM: OMAP2+: Convert SMC91x to use gpmc_cs_program_settings()

Convert the OMAP2+ SMC91x code to use the gpmc_cs_program_settings()
function for configuring the various GPMC options instead of directly
programming the CONFIG1 register.

Move configuration of the GPMC settings outside retime function and
this does not need to be done if the timings are changed dynamically
at runtime.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>