Improve documentation of some SRAM routines

[SatoMew]

The original names for the routines come from these commits: 6faafde and 4571f81. They are a bit confusing since Yellow doesn't have an RTC.

This PR also syncs pokeyellow with pokegold and pokecrystal a bit.

[SatoMew]

@Rangi42 Thanks, I implemented your suggestions. Did I understand them correctly?

[SatoMew]

Should ld a, $1 here be ld a, SRAM_BANKING_MODE or ld a, BANK("Save Data")? This will later be synced with pokered, too.

pokeyellow/engine/menus/main_menu.asm

Lines 278 to 288 in abc3475

	CheckForPlayerNameInSRAM:
	; Check if the player name data in SRAM has a string terminator character
	; (indicating that a name may have been saved there) and return whether it does
	; in carry.
	ld a, SRAM_ENABLE
	ld [MBC1SRamEnable], a
	ld a, $1
	ld [MBC1SRamBankingMode], a
	ld [MBC1SRamBank], a
	ld b, NAME_LENGTH
	ld hl, sPlayerName

[aaaaaa123456789]

  ld a, SRAM_BANKING_MODE
  ld [MBC1SRamBankingMode], a
  assert SRAM_BANKING_MODE == BANK("Save Data")
  ld [MBC1SRamBank], a

[SatoMew]

Thank you, that's an elegant solution! ^^

[SatoMew]

@dannye Done, thanks.