Fix linker relocation overflow errors for the NEC vr4300/ddb toolchain.

Fix linker relocation overflow errors for the NEC vr4300/ddb toolchain.
These changes are related to Ian's gas/libgloss changes of Dec 13/Dec 18.
	* tc-mips.c (mips_ip): If configured for an embedded ELF system,
	don't set the section alignment to 2**4.
	* mips/ddb.ld: Align the location counter before setting _gp, and
	before setting edata.  Remove ALIGN from _gp computation.
	* mips/idt.ld, mips/pmon.ld: Before setting _gp, use ALIGN(8) instead
	of ALIGN(16).  Remove ALIGN from _gp computation.