Fix warnings about deprecated mnemonics on newer builds of rgbds

[Pokechu22]

This fixes warnings like

warning: src/main.asm(4) -> engine/home.asm(808):
	'JP [HL]' is obsolete, use 'JP HL' instead.

and

warning: src/main.asm(4) -> engine/home.asm(971):
	'LD HL,[SP+e8]' is obsolete, use 'LD HL,SP+e8' instead.

on new builds of RGBDS. Everything still compiles correctly with older versions (tested v0.2.5), at least as far as I can tell (I am not familiar with this toolchain).

See also: pret/pokered#147

[dannye]

Thanks!