tegra124: enable flow control for APBDMA in SPI driver

This enables flow control and sets the REQ_SEL field according
to the SPI bus.

Since REQ_SEL is just a constant that is associated with each
channel, a member is added to the tegra_spi_regs struct to hold
the appropriate value.

BUG=none
BRANCH=none
TEST=built and booted on Nyan
Signed-off-by: David Hendricks <dhendrix@chromium.org>

Change-Id: I037aee7e2d422e24a4cbcbc75280ec3c93d3e7bd
Reviewed-on: https://chromium-review.googlesource.com/175630
Reviewed-by: Julius Werner <jwerner@chromium.org>
Commit-Queue: David Hendricks <dhendrix@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>
2 files changed