realtek: 6.12: relocate R4K deactivation to late CPU init

realtek: 6.12: relocate R4K deactivation to late CPU init

To avoid unneeded interrupts the R4K timer is deactivated during
secondary cpu initialization. This is currently done during
phase init_secondary(). With the upgrade to 6.12 the kernel runs
a primary/secondary cpu timer/counter synchronization to verify the
proper setup in synchronise_count_slave(). That runs at a later
point in time and expects the secondary counter to be fully
functional. Finding a deactivated counter results in the following
messages:

WARNING: CPU: 1 PID: 0 at arch/mips/kernel/sync-r4k.c:99 check_counter_warp+0x220/0x254
Warning: zero counter calibration delta: 0 [max: 6500000]
Counter synchronization [CPU#0 -> CPU#1]:
Measured 278760029 cycles counter warp between CPUs

Relocate the deactivation to smp_finsh() at the end of the cpu
startup sequence. Additionally polish the startup code and remove
all unneeded parts.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/18935
Signed-off-by: Robert Marko <robimarko@gmail.com>