serial: fsl_lpuart: fix maximum acceptable baud rate with over-sampling

serial: fsl_lpuart: fix maximum acceptable baud rate with over-sampling

BugLink: https://bugs.launchpad.net/bugs/1837813
[ Upstream commit 815d835b7ba46685c316b000013367dacb2b461b ]

Using over-sampling ratio, lpuart can accept baud rate upto uartclk / 4.

Signed-off-by: Tomonori Sakita <tomonori.sakita@sord.co.jp>
Signed-off-by: Atsushi Nemoto <atsushi.nemoto@sord.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>