amd64_edac: Use DBAM_DIMM macro

Instead of open-coding it, use the DBAM_DIMM macro in
amd64_csrow_nr_pages() which we have already.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>

drivers/edac/amd64_edac.c

@@ -2094,7 +2094,7 @@ static u32 amd64_csrow_nr_pages(struct amd64_pvt *pvt, u8 dct, int csrow_nr)
 	 * number of bits to shift the DBAM register to extract the proper CSROW
 	 * field.
 	 */
-	cs_mode =  (dbam >> ((csrow_nr / 2) * 4)) & 0xF;
+	cs_mode = DBAM_DIMM(csrow_nr / 2, dbam);
 
 	nr_pages = pvt->ops->dbam_to_cs(pvt, dct, cs_mode) << (20 - PAGE_SHIFT);
 

drivers/edac/amd64_edac.h

@@ -219,7 +219,7 @@
 #define DBAM1				0x180
 
 /* Extract the DIMM 'type' on the i'th DIMM from the DBAM reg value passed */
-#define DBAM_DIMM(i, reg)		((((reg) >> (4*i))) & 0xF)
+#define DBAM_DIMM(i, reg)		((((reg) >> (4*(i)))) & 0xF)
 
 #define DBAM_MAX_VALUE			11