Fix the calculation of clear_offset, which may overflow the end of
the buffer. However, this is harmless if it does because in that case
it will be recalculated when we copy the chunk of messages at the
start of the buffer.
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/E1sBsxi-00E8vQ-5r@rmk-PC.armlinux.org.uk