serial: cpm_uart: Deduplicate cpm_line_cr_cmd()

cpm_line_cr_cmd() is identical for CPM1 and CPM2 and
is used only in cpm_uart_core.c. Move it there.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/6996e6ff93067dcddebf0d0c86487345149e165c.1691068700.git.christophe.leroy@csgroup.eu


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>