staging: most: usb: sanity check channel before using it as an index into arrays

Currently channel is being sanity checked after it has been used as
an index into some arrays. Fix this by moving the sanity check of
channel before the arrays are indexed with it.

Addresses-Coverity: ("Negative array index read")
Fixes: 59ed0480 ("Staging: most: replace pr_*() functions by dev_*()")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20200507150652.52238-1-colin.king@canonical.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>