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

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 <[e-mail]>
Reported-by: Junrui Luo <[e-mail]>
Fixes: 35f0ce032b0f ("IBM Real-Time "SMI Free" mode driver -v7")
Signed-off-by: Junrui Luo <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Reviewed-by: Ilpo Järvinen <[e-mail]>
Signed-off-by: Ilpo Järvinen <[e-mail]>

drivers/platform/x86/ibm_rtl.c

···
 	/* 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;