drivers: misc: Add socfpga_dtreg driver for Intel SoCFPGA

Add socfpga_dtreg driver enablement for Intel SoCFPGA.

Signed-off-by: Wan Yee Lau <wan.yee.lau@intel.com>
Reviewed-by: Tien Fong Chee <tien.fong.chee@intel.com>