usb:xusbps-dr-of: Reset phy on initialization

Pulse the USB ULPI phy reset pin before trying to talk to the phy. This seems to
fix the occasional USB problems that were observed on some boards.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
iio: Add data_available callback for buffers

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
iio: kfifo_buf: Implement data_available() callback

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
iio: Add support for blocking IO

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
iio: buffer: rename read_first_n callback to read

It is kind of implied that 'read' will read the first n bytes and not e.g. bytes
only from offsets within the buffer that are a prime number.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
iio: Add output buffer support

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
iio:kfifo: Add output buffer support

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
iio: Add buffer enable/disable callbacks

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
iio: Add dma buffer and mmap support

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>