coresight: STM: Clean up __iomem type usage

The casting and other things here is odd, and causes sparse to
complain:

drivers/hwtracing/coresight/coresight-stm.c:279:35: warning: incorrect type in argument 1 (different address spaces)
drivers/hwtracing/coresight/coresight-stm.c:279:35:    expected void [noderef] <asn:2>*addr
drivers/hwtracing/coresight/coresight-stm.c:279:35:    got struct stm_drvdata *drvdata
drivers/hwtracing/coresight/coresight-stm.c:327:17: warning: incorrect type in argument 2 (different address spaces)
drivers/hwtracing/coresight/coresight-stm.c:327:17:    expected void volatile [noderef] <asn:2>*addr
drivers/hwtracing/coresight/coresight-stm.c:327:17:    got void *addr
drivers/hwtracing/coresight/coresight-stm.c:330:17: warning: incorrect type in argument 2 (different address spaces)
drivers/hwtracing/coresight/coresight-stm.c:330:17:    expected void volatile [noderef] <asn:2>*addr
drivers/hwtracing/coresight/coresight-stm.c:330:17:    got void *addr
drivers/hwtracing/coresight/coresight-stm.c:333:17: warning: incorrect type in argument 2 (different address spaces)
drivers/hwtracing/coresight/coresight-stm.c:333:17:    expected void volatile [noderef] <asn:2>*addr
drivers/hwtracing/coresight/coresight-stm.c:333:17:    got void *addr

>From what I can tell, we don't really need to treat ch_addr as
anything besides a pointer, and we can just do pointer math
instead of ORing in the bits of the offset and achieve the same
thing.

Also, we were passing a drvdata pointer to the
coresight_timeout() function, but we really wanted to pass the
address of the register base. Luckily the base is the first
member of the structure, so everything works out, but this is
quite unsafe if we ever change the structure layout. Clean this
all up so sparse stops complaining on this code.

Reported-by: Satyajit Desai <sadesai@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>