TSA consumers in CPM1 implementation don't need to know about the serial
device number used by the TSA component. In QUICC Engine implementation,
this information is needed.

Improve the TSA API with tsa_serial_get_num() in order to provide this
information.
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/20240808071132.149251-17-herve.codina@bootlin.comSigned-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>