ddr: altera: Move struct sdram_prot_rule prototype

Move the structure prototype from sdram.h header file into sdram.c
source file, since it is used only there and for local purpose only.
There is no point in having it global.

While at this move, fix the data types in the structure from uintNN_t
to uNN and fix the coding style a bit.

Signed-off-by: Marek Vasut <marex@denx.de>