context_tracking: Always inline ct_{nmi,irq}_{enter,exit}()

Thanks to CONFIG_DEBUG_SECTION_MISMATCH, empty functions can be
generated out of line.  These can be called from noinstr code, so make
sure they're always inlined.

Fixes the following warnings:

  vmlinux.o: warning: objtool: irqentry_nmi_enter+0xa2: call to ct_nmi_enter() leaves .noinstr.text section
  vmlinux.o: warning: objtool: irqentry_nmi_exit+0x16: call to ct_nmi_exit() leaves .noinstr.text section
  vmlinux.o: warning: objtool: irqentry_exit+0x78: call to ct_irq_exit() leaves .noinstr.text section

Fixes: 6f0e6c15 ("context_tracking: Take IRQ eqs entrypoints over RCU")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/8509bce3f536bcd4ae7af3a2cf6930d48c5e631a.1743481539.git.jpoimboe@kernel.org
Closes: https://lore.kernel.org/d1eca076-fdde-484a-b33e-70e0d167c36d@infradead.org