mainboard/{iwill,amd/serenget_*}: Fix ptr discards const qualifier

Change-Id: I22e55eb2b7fe06c416e5e4fd322045bc7031ed63
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7693
Tested-by: build bot (Jenkins)
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>

src/mainboard/amd/serengeti_cheetah/acpi_tables.c

@@ -126,7 +126,7 @@ unsigned long mainboard_write_acpi_tables(unsigned long start, acpi_rsdp_t *rsdp
 {
 	unsigned long current;
 	acpi_header_t *ssdtx;
-	void *p;
+	const void *p;
 
 	int i;
 

src/mainboard/amd/serengeti_cheetah_fam10/acpi_tables.c

@@ -135,7 +135,7 @@ unsigned long mainboard_write_acpi_tables(unsigned long current,
 					  acpi_rsdp_t *rsdp)
 {
 	acpi_header_t *ssdtx;
-	void *p;
+	const void *p;
 
 	int i;
 

src/mainboard/iwill/dk8_htx/acpi_tables.c

@@ -133,7 +133,7 @@ unsigned long mainboard_write_acpi_tables(unsigned long start, acpi_rsdp_t *rsdp
 {
 	unsigned long current;
 	acpi_header_t *ssdtx;
-	void *p;
+	const void *p;
 
 	int i;