wifi: mt76: mt7996: extend flexibility of mt7996_mcu_get_eeprom()

wifi: mt76: mt7996: extend flexibility of mt7996_mcu_get_eeprom()

Support passing customized buffer pointer and length to
mt7996_mcu_get_eeprom().

This is the preparation for adding more variants support which needs to
prefetch FEM module from efuse, and also fixes potential OOB issue when
reading the last efuse block.

Co-developed-by: StanleyYP Wang <StanleyYP.Wang@mediatek.com>
Signed-off-by: StanleyYP Wang <StanleyYP.Wang@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Tested-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/20240926032440.15978-1-shayne.chen@mediatek.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>