cpufreq: sti-cpufreq: Fix some formatting and misspelling issues

Kerneldoc format for attribute descriptions should be '@.*: '.

Fixes the following W=1 kernel build warning(s):

 drivers/cpufreq/sti-cpufreq.c:49: warning: cannot understand function prototype: 'struct sti_cpufreq_ddata '

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Pal Singh <ajitpal.singh@st.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>