buildroot

imx-codec: bump to version 4.2.1, enable on AArch64

Changelog:
1. Upgrade EULA to v18
2. Bugfix/Optimization
 - AACPlus: fixed playbe silence after 1s of stream
 - Removed duplicated code in aac_dec/aacplus_dec.
 - Removed unused code in flac_dec.

Note that this package now includes AARCH64 libraries for the upcoming
i.MX8 CPU family.

Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>