drivers: ddr: altera: iossm_mailbox: widen MEM_TOTAL_CAPACITY mask

drivers: ddr: altera: iossm_mailbox: widen MEM_TOTAL_CAPACITY mask

The previous mask for MEM_TOTAL_CAPACITY_INTF was limited to 8 bits,
which could truncate DDR size values on larger-memory systems.

Update INTF_CAPACITY_GBITS_MASK to 32 bits to correctly represent
the full capacity field according to the hardware specification.

Signed-off-by: Naresh Kumar Ravulapalli <nareshkumar.ravulapalli@altera.com>
Signed-off-by: Chen Huei Lok <chen.huei.lok@altera.com>
Reviewed-by: Tien Fong Chee <tien.fong.chee@altera.com> Best regards,