[45/77] Make extract_left_shift take a scalar_int_mode

This patch passes the mode of the shifted value to extract_left_shift
and updates the only caller so that the mode is a scalar_int_mode.

2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* combine.c (extract_left_shift): Add a mode argument and update
	recursive calls.
	(make_compound_operation_int): Change the type of the mode parameter
	to scalar_int_mode and update the call to extract_left_shift.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r251497