wifi: rtlwifi: avoid stack size warning for _read_eeprom_info

txpower_info_{2g,5g} are too big to fit on the stack, but in most of the
rtlwifi variants this stays below the warning limit for stack frames.
In rtl8192ee and a few others, I see a case where clang decides to fully
inline this into rtl92ee_read_eeprom_info, triggering this warning:

drivers/net/wireless/realtek/rtlwifi/rtl8192ee/hw.c:2178:6: error: stack frame size (1312) exceeds limit (1280) in 'rtl92ee_read_eeprom_info' [-Werror,-Wframe-larger-than]

Mark _rtl92ee_read_txpower_info_from_hwpg() as noinline_for_stack to
and mark _rtl92ee_get_chnl_group() as __always_inline to make clang
behave the same way as gcc. Inlining _rtl92ee_get_chnl_group helps
let the compiler see that the index is always in range. The same
change appears to be necessary in all rtlwifi variants.

A more thorough approach would be to avoid the use of the two structures
on the stack entirely and combine them with the struct rtl_efuse
data that is dynamically allocated and holds the same information.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250610092240.2639751-1-arnd@kernel.org