x86: get rid of 'rtype' argument to __get_user_asm() macro

This is the exact same thing as 36807856 ("x86: get rid of 'rtype'
argument to __put_user_goto() macro") except it's about __get_user_asm()
rather than __put_user_goto().

The reasons are the same: having the low-level asm access the argument
with a different size than the compiler thinks it does is fundamentally
wrong.

But unlike the __put_user_goto() case, we actually did tell the compiler
that we used a bigger variable (either long or long long), and then only
filled in the low bits, and ended up "fixing" this by casting the result
to the proper pointer type.

That's because we needed to use a non-qualified type (the user pointer
might be a const pointer!), and that makes this a bit more painful.  Our
'__inttype()' macro used to be lazy and only differentiate between "fits
in a register" or "needs two registers".

So this fix had to also make that '__inttype()' macro more precise.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>