usb: bdc: remove duplicated error message

in case devm_platform_ioremap_resource() fails, that function already
prints a relevant error message which renders the driver's dev_err()
redundant. Let's remove the unnecessary message and, while at that,
also make sure to pass along the error value returned by
devm_platform_ioremap_resource() instead of always returning -ENOMEM.

Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>

[balbi@kernel.org : improved commit log]

Signed-off-by: Felipe Balbi <balbi@kernel.org>