bluetooth: hci: place tx/rx message buffer in .noinit section

This change relocates the tx/rx message buffer from the .bss section
to the .noinit section. This adjustment is aimed at reducing boot time by
lowering the size of the .bss section, without impacting the operational
functionality of the buffer.

Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>