mmc: increase MMC SDHCI read status timeout

Otherwise,  ocassionally see errors like this:
  Flashing sparse image at offset 2078720
  Flashing Sparse Image
  sdhci_send_command: Timeout for status update!
  mmc fail to send stop cmd
  write_sparse_image: Write failed, block #2181088 [0]

This does not affect the actual writing speed, which is controlled by
the default value:
  CONFIG_SDHCI_CMD_DEFAULT_TIMEOUT

It only increases the retries when reading:
  SDHCI_INT_STATUS
to avoid the timeout error.

Signed-off-by: Steve Rae <steve.rae@raedomain.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Jaehoon Chung <jh80.chung@samsung.com>