usb: vhci-hcd: Replace pr_*() with dev_*() logging

usb: vhci-hcd: Replace pr_*() with dev_*() logging

Where possible, use driver model logging helpers dev_*() instead of
pr_*() to ensure the messages are always associated with the
corresponding device/driver.

While at it, join the split strings to make checkpatch happy and regain
ability to grep for those log messages in the source code:

  WARNING: quoted string split across lines

Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://lore.kernel.org/r/20251008-vhci-hcd-cleanup-v2-2-b6acc4dd6e44@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>