mmc: msm_sdcc: Driver clocking/irq improvements

- Clocks are now disabled after 1 second of inactivity
- Fixed issue which was causing us to loop through our ISR twice
- Bump core clock enable delay to 30us

Signed-off-by: San Mehat <san@google.com>
Signed-off-by: Daniel Walker <dwalker@codeaurora.org>