platform/x86: ibm_rtl: fix EBDA signature search pointer arithmetic

[ Upstream commit 15dd100349b8526cbdf2de0ce3e72e700eb6c208 ]

The ibm_rtl_init() function searches for the signature but has a pointer
arithmetic error. The loop counter suggests searching at 4-byte intervals
but the implementation only advances by 1 byte per iteration.

Fix by properly advancing the pointer by sizeof(unsigned int) bytes
each iteration.

Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Reported-by: Junrui Luo <moonafterrain@outlook.com>
Fixes: 35f0ce0 ("IBM Real-Time "SMI Free" mode driver -v7")
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
Link: https://patch.msgid.link/SYBPR01MB78812D887A92DE3802D0D06EAFA9A@SYBPR01MB7881.ausprd01.prod.outlook.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Ulrich Hecht <uli@kernel.org>

Author: avasummer

drivers/platform/x86/ibm_rtl.c

@@ -276,7 +276,7 @@ static int __init ibm_rtl_init(void) {
 	/* search for the _RTL_ signature at the start of the table */
 	for (i = 0 ; i < ebda_size/sizeof(unsigned int); i++) {
 		struct ibm_rtl_table __iomem * tmp;
-		tmp = (struct ibm_rtl_table __iomem *) (ebda_map+i);
+		tmp = (struct ibm_rtl_table __iomem *) (ebda_map + i*sizeof(unsigned int));
 		if ((readq(&tmp->signature) & RTL_MASK) == RTL_SIGNATURE) {
 			phys_addr_t addr;
 			unsigned int plen;