[MIPS] Drop __devinit tag from allocate_irqno() and free_irqno()

This fix these warnings:

WARNING: arch/mips/kernel/built-in.o - Section mismatch: reference to .init.text:free_irqno from __ksymtab_gpl between '__ksymtab_free_irqno' (at offset 0x0) and '__ksymtab_allocate_irqno'
WARNING: arch/mips/kernel/built-in.o - Section mismatch: reference to .init.text:allocate_irqno from __ksymtab_gpl after '__ksymtab_allocate_irqno' (at offset 0x8)

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>