staging: dwc2: Make dwc2_hw_params.host_channels large enough

The hardware offers a 4-bit register containing the number of host
channels. However, the values of these register mean 1-16 host channels,
not 0-15. Since the dwc2_hw_params struct stores the actual number of
host channels supported instead of the raw register value, it should be
5 bits wide instead of 4.

Before this commit, hardware with 16 host channels would overflow the
field, making it appear as 0 channels.

This bug was introduced in commit 9badec2f (staging: dwc2: interpret all
hwcfg and related register at init time).

Reported-by: Dinh Nguyen <dinguyen@altera.com>
Signed-off-by: Matthijs Kooijman <matthijs@stdin.nl>
Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>