This appears to be a copy and paste error. The UART size was used
instead of the much smaller OMPIC size. But actually that smaller OMPIC
size is wrong too and doesn't allow the IPI to work in Linux. So set it
to the old value.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
[smh:Updated OR1KSIM_OMPIC size to use OR1KSIM_CPUS_MAX]
Signed-off-by: Stafford Horne <shorne@gmail.com>