rt2x00: convert rt2800_eeprom_read return type

This is a semi-automated conversion to change rt2800_eeprom_read to return
the register contents instead of passing them by value, resulting in
much better object code. The majority of the patch was done using:

sed -i 's:\(\<rt2800_eeprom_read\(_from_array\|\)\>(.*, .*\), &\(.*\));:\3 = \1);:'
	drivers/net/wireless/ralink/rt2x00/rt2800lib.c

Some manual tweaking was required here to work around the line wraps.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>