cpufreq: OMAP: Fix compilation error 'r & ret undeclared'

With a recent change "d4019f0a cpufreq: move freq change notifications to cpufreq
core" few variables (r & ret) are removed by mistake and hence these warnings:

drivers/cpufreq/omap-cpufreq.c: In function omap_target:
drivers/cpufreq/omap-cpufreq.c:64:2: error: ret undeclared (first use in this function)
drivers/cpufreq/omap-cpufreq.c:64:2: note: each undeclared identifier is reported only once for each function it appears in
drivers/cpufreq/omap-cpufreq.c:94:3: error: r undeclared (first use in this function)
drivers/cpufreq/omap-cpufreq.c:116:1: warning: control reaches end of non-void function [-Wreturn-type]

Lets fix them by declaring those variables again.

Fixes: d4019f0a

 (cpufreq: move freq change notifications to cpufreq core)
Reported-by: Sebastian Capella <sebastian.capella@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>