ARM: shmobile: defconfig: Refresh for v6.7-rc1

Refresh the defconfig for Renesas ARM systems:
  - Disable CONFIG_SERIAL_8250_EXAR (auto-enabled since commit
    5939ff7f ("tty: serial: 8250_exar: Does not use anything
    from 8250_pci")).
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/b9bdb0fe3635a7eb51a7eca9a06e8146d6ad82db.1700667824.git.geert+renesas@glider.be

arch/arm/configs/shmobile_defconfig

@@ -75,6 +75,7 @@ CONFIG_SERIAL_8250=y
 # CONFIG_SERIAL_8250_16550A_VARIANTS is not set
 CONFIG_SERIAL_8250_CONSOLE=y
 # CONFIG_SERIAL_8250_PCI is not set
+# CONFIG_SERIAL_8250_EXAR is not set
 CONFIG_SERIAL_8250_DW=y
 CONFIG_SERIAL_8250_EM=y
 # CONFIG_SERIAL_8250_PERICOM is not set