ARM: OMAP2+: Fix out of range register access with syscon_config.max_register

If syscon_config.max_register is initialized like it should be, we have
omap_ctrl_read/write() fail with out of range register access at least
for omap3.

We have omap3.dtsi setting up a regmap range for scm_conf, but we now
have omap_ctrl_read/write() also attempt to use the regmap. However,
omap_ctrl_read/write() is also used for other register ranges in the
system control module (SCM).

Let's fix the issue by just removing the regmap_read/write() usage for
control module as suggested by Tero Kristo <t-kristo@ti.com>.

Signed-off-by: Tony Lindgren <tony@atomide.com>