regmap: cache: Revert "Add 64-bit mode support"

There is no support for 64-bit data size in regmap, so
there is no point to have it in regmap cache.

This reverts commit 8b7663de.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230622183613.58762-3-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/regcache.c

@@ -590,14 +590,6 @@ void regcache_set_val(struct regmap *map, void *base, unsigned int idx,
 		cache[idx] = val;
 		break;
 	}
-#ifdef CONFIG_64BIT
-	case 8: {
-		u64 *cache = base;
-
-		cache[idx] = val;
-		break;
-	}
-#endif
 	default:
 		BUG();
 	}
@@ -630,13 +622,6 @@ unsigned int regcache_get_val(struct regmap *map, const void *base,
 
 		return cache[idx];
 	}
-#ifdef CONFIG_64BIT
-	case 8: {
-		const u64 *cache = base;
-
-		return cache[idx];
-	}
-#endif
 	default:
 		BUG();
 	}