gpio: Add support for stmpe variant 801

STMPE801 is a GPIO expander. GPIO registers for 801 are slightly different from other
variants. This patch adds support for STMPE801 in stmpe gpio driver.

Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
Signed-off-by: Pratyush Anand <pratyush.anand@st.com>
Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>