This patch fixes the MISRA-C violations related to mmio_read**
* add `const` qualifier in implementation of mmio_read**
`const` qualifier shall be added
Tracked-On: #861
Signed-off-by: Shiqing Gao <shiqing.gao@intel.com>
Reviewed-by: Eddie Dong <eddie.dong@intel.com>
Reviewed-by: Li, Fei1 <fei1.li@intel.com>