ddr: altera: sequencer: Zap bogus redefinition of RW_MGR_MEM_NUMBER_OF_RANKS

This is defined in the QTS-generated headers, so it must not be
re-defined in sequencer.h .

Signed-off-by: Marek Vasut <marex@denx.de>
Acked-by: Dinh Nguyen <dinguyen@opensource.altera.com>