MIPS: Bugfix for fix Dejagnu issues with RTL checking enabled.

gcc/ChangeLog:

	* config/mips/mips.cc (mips_set_text_contents_type): Use HOST_WIDE_INT
	instead of long.
	* config/mips/mips-protos.h (mips_set_text_contents_type): Likewise.

Signed-off-by: Xin Liu <xin.liu@oss.cipunited.com>