mmc: Restructure polling loops to avoid extra delays

The polling loops in sd_send_op_cond and mmc_complete_op_cond functions
check the ready flag state at the end of the loop, that is after executing
a delay inside the loop, which, in case of exiting with no error,
is not needed. Also, one of these loops, as well as the loop
in mmc_send_status, have the delay just before exiting on timeout
conditions.

Restructure all these loops to check the respective conditions before making
a delay for the next loop pass, and to appropriately exit without the delay.

Signed-off-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>