EDAC/bluefield: Fix potential integer overflow

The 64-bit argument for the "get DIMM info" SMC call consists of mem_ctrl_idx
left-shifted 16 bits and OR-ed with DIMM index.  With mem_ctrl_idx defined as
32-bits wide the left-shift operation truncates the upper 16 bits of
information during the calculation of the SMC argument.

The mem_ctrl_idx stack variable must be defined as 64-bits wide to prevent any
potential integer overflow, i.e. loss of data from upper 16 bits.

Fixes: 82413e56 ("EDAC, mellanox: Add ECC support for BlueField DDR4")
Signed-off-by: David Thompson <davthompson@nvidia.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shravan Kumar Ramani <shravankr@nvidia.com>
Link: https://lore.kernel.org/r/20240930151056.10158-1-davthompson@nvidia.com