Add flash driver for it8xxx2. The driver can implement
flash read, write and erase that will be mapped to the
ram section for executing.
TEST="flash write 0x80000 0x10 0x20 0x30 0x40 ..."
"flash read 0x80000 0x100"
"flash erase 0x80000 0x1000"
Signed-off-by: Tim Lin <tim2.lin@ite.corp-partner.google.com>
Tim Lin