net: macb: avoid dealing with endianness in macb_set_hwaddr()

bp->dev->dev_addr is of type `unsigned char *`. Casting it to a u32
pointer and dereferencing implies dealing manually with endianness,
which is error-prone.

Replace by calls to get_unaligned_le32|le16() helpers.

This was found using sparse:
   ⟩ make C=2 drivers/net/ethernet/cadence/macb_main.o
   warning: incorrect type in assignment (different base types)
      expected unsigned int [usertype] bottom
      got restricted __le32 [usertype]
   warning: incorrect type in assignment (different base types)
      expected unsigned short [usertype] top
      got restricted __le16 [usertype]
   ...

Reviewed-by: Sean Anderson <sean.anderson@linux.dev>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250923-macb-fixes-v6-5-772d655cdeb6@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: tleb

drivers/net/ethernet/cadence/macb_main.c

@@ -274,9 +274,9 @@ static void macb_set_hwaddr(struct macb *bp)
 	u32 bottom;
 	u16 top;
 
-	bottom = cpu_to_le32(*((u32 *)bp->dev->dev_addr));
+	bottom = get_unaligned_le32(bp->dev->dev_addr);
 	macb_or_gem_writel(bp, SA1B, bottom);
-	top = cpu_to_le16(*((u16 *)(bp->dev->dev_addr + 4)));
+	top = get_unaligned_le16(bp->dev->dev_addr + 4);
 	macb_or_gem_writel(bp, SA1T, top);
 
 	if (gem_has_ptp(bp)) {