rtc-mxc: multiple fixes in rtc-mxc probe method

On exit paths in mxc_rtc_probe() method some resources are not freed
correctly.

This patch fixes:
* unrequested memory region containing imx RTC registers
* iounmap() isn't called on exit_free_pdata branch
* clock get rate is called for freed clock source
* clock isn't disabled on exit_put_clk branch

To simplify the fix managed device resources are used.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Vladimir Zapolskiy <vzapolskiy@gmail.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>