nvmem: imx: scu: support hole region check

Introduce HOLE/ECC_REGION flag and in_hole helper to ease the check
of hole region. The ECC_REGION is also introduced here which is
preparing for programming support. ECC_REGION could only be programmed
once, so need take care.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>