powerpc/64: Init jump labels before parse_early_param()

In the Linux kernel, the following vulnerability has been resolved:

powerpc/64: Init jump labels before parse_early_param()

On 64-bit, calling jump_label_init() in setup_feature_keys() is too

late because static keys may be used in subroutines of

parse_early_param() which is again subroutine of early_init_devtree().

For example booting with "threadirqs":

static_key_enable_cpuslocked(): static key '0xc000000002953260' used before call to jump_label_init()

WARNING: CPU: 0 PID: 0 at kernel/jump_label.c:166 static_key_enable_cpuslocked+0xfc/0x120

...

NIP static_key_enable_cpuslocked+0xfc/0x120

LR static_key_enable_cpuslocked+0xf8/0x120

Call Trace:

static_key_enable_cpuslocked+0xf8/0x120 (unreliable)

static_key_enable+0x30/0x50

setup_forced_irqthreads+0x28/0x40

do_early_param+0xa0/0x108

parse_args+0x290/0x4e0

parse_early_options+0x48/0x5c

parse_early_param+0x58/0x84

early_init_devtree+0xd4/0x518

early_setup+0xb4/0x214

So call jump_label_init() just before parse_early_param() in

early_init_devtree().

[mpe: Add call trace to change log and minor wording edits.]