firmware: Add the support for ZSTD-compressed firmware files

firmware: Add the support for ZSTD-compressed firmware files

As the growing demand on ZSTD compressions, there have been requests
for the support of ZSTD-compressed firmware files, so here it is:
this patch extends the firmware loader code to allow loading ZSTD
files.  The implementation is fairly straightforward, it just adds a
ZSTD decompression routine for the file expander.  (And the code is
even simpler than XZ thanks to the ZSTD API that gives the original
decompressed size from the header.)

Link: https://lore.kernel.org/all/[email protected]/
Tested-by: Piotr Gorski <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>