target/i386: Rename helper template headers as '.h.inc'

target/i386: Rename helper template headers as '.h.inc'

Since commit 139c1837db ("meson: rename included C source files
to .c.inc"), QEMU standard procedure for included C files is to
use *.c.inc.

Besides, since commit 6a0057aa22 ("docs/devel: make a statement
about includes") this is documented as the Coding Style:

  If you do use template header files they should be named with
  the ``.c.inc`` or ``.h.inc`` suffix to make it clear they are
  being included for expansion.

Therefore move the included templates in the tcg/ directory and
rename as '.h.inc'.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230608133108.72655-5-philmd@linaro.org>