drivers: modem: altair: auto select SPI
The Altair hardware is connected to SPI and will not work without SPI support
The SPI_EXCHANGE is automaticaly enabled (default y) when SPI is selected.
Since SPI is mandatory it should be auto selected
Signed-off-by: Alin Jerpelea <alin.jerpelea@sony.com>
Approved-by: Gregory Nutt <gnutt@nuttx.org>