rtw88: Fix array overrun in rtw_get_tx_power_params()

In the Linux kernel, the following vulnerability has been resolved:

rtw88: Fix array overrun in rtw_get_tx_power_params()

Using a kernel with the Undefined Behaviour Sanity Checker (UBSAN) enabled, the
following array overrun is logged:

================================================================================
UBSAN: array-index-out-of-bounds in /home/finger/wireless-drivers-next/drivers/net/wireless/realtek/rtw88/phy.c:1789:34
index 5 is out of range for type 'u8 [5]'
CPU: 2 PID: 84 Comm: kworker/u16:3 Tainted: G O 5.12.0-rc5-00086-gd88bba47038e-dirty #651
Hardware name: TOSHIBA TECRA A50-A/TECRA A50-A, BIOS Version 4.50 09/29/2014
Workqueue: phy0 ieee80211_scan_work [mac80211]
Call Trace:
dump_stack+0x64/0x7c
ubsan_epilogue+0x5/0x40
__ubsan_handle_out_of_bounds.cold+0x43/0x48
rtw_get_tx_power_params+0x83a/drivers/net/wireless/realtek/rtw88/0xad0 [rtw_core]
? rtw_pci_read16+0x20/0x20 [rtw_pci]
? check_hw_ready+0x50/0x90 [rtw_core]
rtw_phy_get_tx_power_index+0x4d/0xd0 [rtw_core]
rtw_phy_set_tx_power_level+0xee/0x1b0 [rtw_core]
rtw_set_channel+0xab/0x110 [rtw_core]
rtw_ops_config+0x87/0xc0 [rtw_core]
ieee80211_hw_config+0x9d/0x130 [mac80211]
ieee80211_scan_state_set_channel+0x81/0x170 [mac80211]
ieee80211_scan_work+0x19f/0x2a0 [mac80211]
process_one_work+0x1dd/0x3a0
worker_thread+0x49/0x330
? rescuer_thread+0x3a0/0x3a0
kthread+0x134/0x150
? kthread_create_worker_on_cpu+0x70/0x70
ret_from_fork+0x22/0x30
================================================================================

The statement where an array is being overrun is shown in the following snippet:

if (rate <= DESC_RATE11M)
tx_power = pwr_idx_2g->cck_base[group];
else
====> tx_power = pwr_idx_2g->bw40_base[group];

The associated arrays are defined in main.h as follows:

struct rtw_2g_txpwr_idx {
u8 cck_base[6];
u8 bw40_base[5];
struct rtw_2g_1s_pwr_idx_diff ht_1s_diff;
struct rtw_2g_ns_pwr_idx_diff ht_2s_diff;
struct rtw_2g_ns_pwr_idx_diff ht_3s_diff;
struct rtw_2g_ns_pwr_idx_diff ht_4s_diff;
};

The problem arises because the value of group is 5 for channel 14. The trivial
increase in the dimension of bw40_base fails as this struct must match the layout of
efuse. The fix is to add the rate as an argument to rtw_get_channel_group() and set
the group for channel 14 to 4 if rate <= DESC_RATE11M.

This patch fixes commit fa6dfe6bff24 ("rtw88: resolve order of tx power setting routines")