hw/pci-host: remove break after g_assert_not_reached()

Use of assert(false) can trip spurious control flow warnings from
some versions of GCC (i.e. using -fsanitize=thread with gcc-12):

  error: control reaches end of non-void function [-Werror=return-type]
        default:
            g_assert_not_reached();
            break;
          | ^^^^^

Solve that by removing the unreachable 'break' statement, unifying
the code base on g_assert_not_reached() instead.

Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240910221606.1817478-31-pierrick.bouvier@linaro.org>
[PMD: Add description suggested by Eric Blake]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/pci-host/gt64120.c

@@ -689,7 +689,6 @@ static void gt64120_writel(void *opaque, hwaddr addr,
     case GT_PCI0_CFGDATA:
         /* Mapped via in gt64120_pci_mapping() */
         g_assert_not_reached();
-        break;
 
     /* Interrupts */
     case GT_INTRCAUSE:
@@ -933,7 +932,6 @@ static uint64_t gt64120_readl(void *opaque,
     case GT_PCI0_CFGDATA:
         /* Mapped via in gt64120_pci_mapping() */
         g_assert_not_reached();
-        break;
 
     case GT_PCI0_CMD:
     case GT_PCI0_TOR: