Bluetooth: btmrvl: trivial style fixes

Patch shortens locals scope and adds missing braces. This is a diff
between v1 which was applied and v2 of patch "Bluetooth: btmrvl: Do
not send vendor events to bluetooth stack".

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>