dmaengine: edma: Make reading the position of active channels work

As Joel pointed out, edma_read_position() uses memcpy_fromio() to read
the parameter ram. That's not synchronized with the internal update as
it does a byte by byte copy. We need to do a 32bit read to get a
consistent value.

Further reading destination and source is pointless. In DEV_TO_MEM
transfers we are only interested in the destination, in MEM_TO_DEV we
care about the source. In MEM_TO_MEM it really does not matter which
one you read.

Simple solution: Remove the pointers, select dest/source via a bool
and return the read value.

Remove the export of this function while at it. The only potential
user is the dmaengine and that's always builtin.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Joel Fernandes <joelf@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>