tables.h: remove postfix _TEXT for .text sectioned code

The _TEXT postfix is removed to since SECTION_INIT also
implicates .init.text -- stick the convention to default
to .text unless otherwise noted.

References for this decision:

http://lkml.kernel.org/r/20160224005458.GK25240@wotan.suse.de

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>