bluecard_hci_set_baud_rate() is never called in atomic context.

bluecard_hci_set_baud_rate() is only by bluecard_hci_open(), which is
set to hdev->open, and hdev->open() is never called in atomic context.

bluecard_hci_set_baud_rate() calls bt_skb_alloc() with GFP_ATOMIC,
which is not necessary. GFP_ATOMIC can be replaced with GFP_KERNEL.

This is found by a static analysis tool named DCNS written by myself.
I also manually check the kernel code before reporting it.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>