omap: Eliminate OMAP_MAX_NR_PORTS

Eliminate OMAP_MAX_NR_PORTS

Note that also the null terminator entry for omap1
serial_platform_data needs to be now removed to avoid
oopsing.

Signed-off-by: Alexander Shishkin <virtuoso@slind.org>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>