Using a fixed 2s timeout for all commands is a bit problematic.

For some commands it means waiting longer than needed for the timer to
expire, which may not a big issue, but still. For other commands, like for
an erase (CMD38) that uses a R1B response, may require longer timeouts than
2s. In these cases, we may end up treating the command as it failed, while
it just needed some more time to complete successfully.

Fix the problem by respecting the cmd->busy_timeout, which is provided by
the mmc core.

Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Link: https://lore.kernel.org/r/20200414161413.3036-4-ulf.hansson@linaro.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>