imx: bundle correct SDMA firmware for i.MX 7 boards

Import sdma-imx7d.bin from linux-firmware repository at commit:
55edf5202154: ("imx: sdma: update firmware to v3.5/v4.5")

Cortex-A7 boards (i.MX 7 based) use different SDMA firmware than i.MX 6
boards - bundle the correct files in per-subtarget kernel options.

Signed-off-by: Lech Perczak <lech.perczak@gmail.com>