Add 'no ual' macros for GBA

[mkst]

Creating an issue to track a discussion on discord between mkst/mono/lunar.

.macro arm_func_start_no_ual name
    .arm
.endm
.macro thumb_func_start_no_ual name
    .thumb
.endm
.macro arm_func_start name
    .arm
    .syntax unified
.endm
.macro thumb_func_start name
    .thumb
    .syntax unified
.endm

We could/should also look at providing CAPITALISED version of these macros (at least THUMB_FUNC_START)