ARM: shmobile: defconfig: Refresh for v6.18-rc1

ARM: shmobile: defconfig: Refresh for v6.18-rc1

Refresh the defconfig for Renesas ARM systems:
  - Drop CONFIG_SCHED_MC=y (auto-enabled since commit 7bd291abe2da09f5
    ("sched: Unify the SCHED_{SMT,CLUSTER,MC} Kconfig")),
  - Disable CONFIG_SCHED_SMT (auto-enabled since commit 7bd291abe2da09f5
    ("sched: Unify the SCHED_{SMT,CLUSTER,MC} Kconfig")),
  - Restore CONFIG_ARM_GT_INITIAL_PRESCALER_VAL=1 (default changed to
    zero (auto-detect) in commit 1c4b87c921fb158d
    ("clocksource/drivers/arm_global_timer: Add auto-detection for
    initial prescaler values")),
  - Disable CONFIG_RPCSEC_GSS_KRB5 (auto-enabled since commit
    d8e97cc476e33037 ("SUNRPC: Make RPCSEC_GSS_KRB5 select CRYPTO
    instead of depending on it")).

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/d0fcc82fb294021bf96f8a490234165e15aadb43.1760530468.git.geert+renesas@glider.be