ARM: omap2: pmic-cpcap: fix maximum voltage to be consistent with defaults on xt875

xt875 comes up with a iva voltage of 1375000 and android runs at this too. fix
maximum voltage to be consistent with this.

Signed-off-by: Carl Philipp Klemm <philipp@uvos.xyz>
Signed-off-by: Tony Lindgren <tony@atomide.com>