drivers: serial: stm32: renable IT RXNE as part of graceful disable
drivers: serial: stm32: renable IT RXNE as part of graceful disable

async_rx_disable does not re-anable RXNE interrupt, it was disabled
during async_rx_enable

Signed-off-by: Manojkumar Subramaniam <e5bed78df35c9a68cd0ebc89592def76df34c305@electrolance.com>

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