ARM: OMAP2+: remove obsolete config OMAP3_SDRC_AC_TIMING

Commit d42f265a ("ARM: OMAP3: clock: remove un-used core dpll
re-program code") removes arch/arm/mach-omap2/sram34xx.S, which
implemented the effect of the config OMAP3_SDRC_AC_TIMING. Since then, the
OMAP3_SDRC_AC_TIMING config was hanging around without effect.

Remove this obsolete config.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Message-Id: <20230320083806.9545-1-lukas.bulwahn@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>