thunk: Drop unused NO_THUNK_TYPE_SIZE guards

The thunk_type_size_array() and thunk_type_align_array() functions
are only provided if NO_THUNK_TYPE_SIZE is not defined. However
nothing in the codebase defines that, and so in fact these functions
are always present. Drop the unnecessary #ifdefs.

(Over a decade ago thunk.h used to be included by some softmmu
files, which defined NO_THUNK_TYPE_SIZE, but these includes are
long gone; see for instance commit f193c7979c2f7.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
