ALSA: usb-audio: Increase max buffer size

ALSA: usb-audio: Increase max buffer size

BugLink: https://bugs.launchpad.net/bugs/1969857
[ Upstream commit fee2ec8cceb33b8886bc5894fb07e0b2e34148af ]

The current limit of max buffer size 1MB seems too small for modern
devices with lots of channels and high sample rates.
Let's make bigger, 4MB.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220407212740.17920-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>