ARM: dts: stm32: fix AV96 board SAI2 pin muxing on stm32mp15

commit ee2aacb6 upstream.

Replace sai2a-2 node name by sai2a-sleep-2, to avoid name
duplication.

Fixes: 1a9a9d22 ("ARM: dts: stm32: fix AV96 board SAI2 pin muxing on stm32mp15")

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Marek Vasut <marex@denx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>