hw/mips/gt64xxx: Simplify ISD MemoryRegion read/write handlers

The ISD MemoryRegion is implemented for 32-bit accesses.
Simplify it by setting the MemoryRegionOps::impl min/max
access size fields.

Since the region is registered with a size of 0x1000 bytes,
we can remove the hwaddr mask.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: BALATON Zoltan <balaton@eik.bme.hu>
Message-Id: <20210309142630.728014-3-f4bug@amsat.org>

hw/mips/gt64xxx_pci.c

@@ -385,13 +385,12 @@ static void gt64120_writel(void *opaque, hwaddr addr,
 {
     GT64120State *s = opaque;
     PCIHostState *phb = PCI_HOST_BRIDGE(s);
-    uint32_t saddr;
+    uint32_t saddr = addr >> 2;
 
     if (!(s->regs[GT_CPU] & 0x00001000)) {
         val = bswap32(val);
     }
 
-    saddr = (addr & 0xfff) >> 2;
     switch (saddr) {
 
     /* CPU Configuration */
@@ -695,9 +694,8 @@ static uint64_t gt64120_readl(void *opaque,
     GT64120State *s = opaque;
     PCIHostState *phb = PCI_HOST_BRIDGE(s);
     uint32_t val;
-    uint32_t saddr;
+    uint32_t saddr = addr >> 2;
 
-    saddr = (addr & 0xfff) >> 2;
     switch (saddr) {
 
     /* CPU Configuration */
@@ -976,6 +974,10 @@ static const MemoryRegionOps isd_mem_ops = {
     .read = gt64120_readl,
     .write = gt64120_writel,
     .endianness = DEVICE_NATIVE_ENDIAN,
+    .impl = {
+        .min_access_size = 4,
+        .max_access_size = 4,
+    },
 };
 
 static int gt64120_pci_map_irq(PCIDevice *pci_dev, int irq_num)