tools: socfpgaimage: Add param entry point (ep) support for Arria 10 (v1)

Add param entry point (ep) support for Arria 10 header. User can pass in
'e' option to mkimage to set the entry point. This is an optional option.

If not specified, default is 0x14.

Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>