cpumask: Always inline helpers which use bit manipulation functions

Former are always inlined so do that for the latter too, for
consistency.

Size impact is a whopping 5 bytes increase! :-)

   text    data     bss     dec     hex filename
22350551        8213184 1917164 32480899        1ef9e83 vmlinux.x86-64.defconfig.before
22350556        8213152 1917164 32480872        1ef9e68 vmlinux.x86-64.defconfig.after

Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20220113155357.4706-3-bp@alien8.de