vsnprintf: collapse the number format state into one single state

vsnprintf: collapse the number format state into one single state

We'll squirrel away the size of the number in 'struct fmt' instead.

We have two fairly separate state structures: the 'decode state' is in
'struct fmt', while the 'printout format' is in 'printf_spec'.  Both
structures are small enough to pass around in registers even across
function boundaries (ie two words), even on 32-bit machines.

The goal here is to avoid the case statements on the format states,
which generate either deep conditionals or jump tables, while also
keeping the state size manageable.

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