Update KSDK SDHC driver for K64F & K66F

1. Use function pointer for interrupt handler, this should reduce the code-size
   for applications that do not use this driver
2. Fix the wait for initialization of the SD card
3. Fix SDHC driver support for non-word aligned accesses
4. Remove some redundant code & assert function calls.
5. Updated various comments

Signed-off-by: Mahadevan Mahesh <Mahesh.Mahadevan@nxp.com>

Author: mmahadevan108