MFC: r222475
Fix read_ivar implementation for MMC and SD.
- Both mmc_read_ivar() and sdhci_read_ivar() use the expression
'*(int *)result = val' to assign to result which is uintptr_t *.
This does not work on big-endian 64 bit systems.
- The media_size ivar is declared as 'off_t' which does not fit
into uintptr_t in 32bit systems, change this to long.
Submitted by: kanthms at netlogicmicro com (initial version)
PR: 134745