MIPS/GAS/doc: Refer to `.module' rather than `.set'

MIPS/GAS/doc: Refer to `.module' rather than `.set'

Complement commit 919731affbef ("Add MIPS .module directive") and update
the GAS manual to refer to the `.module' rather than `.set' directive in
command-line option descriptions, following an observation that unlike
`.set' and like the respective command-line option the use of the
`.module' directive affects the ISA and ASE flags recorded in the object
file produced, and therefore it is `.module' rather than `.set' that
corresponds to the respective command-line option.

	gas/
	* doc/as.texinfo (-mips16, -no-mips16): Refer to `.module
	mips16' rather than `.set mips16'.
	(-mmicromips, -mno-micromips): Refer to `.module micromips' and
	`.module nomicromips' rather than `.set micromips' and `.set
	nomicromips'.
	(-msmartmips, -mno-smartmips): Refer to `.module smartmips'
	rather than `.set smartmips'.
	* doc/c-mips.texi (MIPS Options): Refer to `.module mips16',
	`.module micromips', `.module nomicromips' and `.module
	smartmips' rather than `.set mips16', `.set micromips', `.set
	nomicromips' and `.set smartmips' respectively.