include/intarith: enforce the same type for p2*() arguments

include/intarith: enforce the same type for p2*() arguments

x and align must be of the same width.  Otherwise the lack of
sign-extension can bite, e.g.:

  uint64_t x = 128000;
  uint32_t align = 32768;
  uint64_t res = p2roundup(x, align);
  // res = 18446744069414715392

While the templates added in commit c06b97b3d7e3 ("include: Add
templates along side macros in intarith") are technically correct,
P2*() macros weren't meant to be used with different types.  The
Solaris kernel (which is where they originated) has P2*_TYPED()
variants for that.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>