Optimize do_register by combining feature check with internal flag

Introduce the new internal flag INT_FLAG_REG_REG_RING, set when setting
INT_FLAG_REG_RING if the kernel supports IORING_FEAT_REG_REG_RING. This
allows all the register functions to just check INT_FLAG_REG_REG_RING.

Suggested-by: Dylan Yudaken <dylany@meta.com>
Signed-off-by: Josh Triplett <josh@joshtriplett.org>
2 files changed