wifi-scripts: fix RX-STBC notation VHT capabilities

wifi-scripts: fix RX-STBC notation VHT capabilities

Notation for RX-STBC VHT capabilities when specifying number of spatial
streams should be hyphenated, e.g. RX-STBC-1, RX-STBC-2. HT capabilities
use without hyphen, e.g. RX-STBC1, RX-STBC2. This is consistent with
what hostapd expects.

```c
static int hostapd_config_ht_capab(struct hostapd_config *conf,
				   const char *capab)
{
	if (os_strstr(capab, "[RX-STBC1]")) {
		conf->ht_capab &= ~HT_CAP_INFO_RX_STBC_MASK;
		conf->ht_capab |= HT_CAP_INFO_RX_STBC_1;
	}
	if (os_strstr(capab, "[RX-STBC12]")) {
		conf->ht_capab &= ~HT_CAP_INFO_RX_STBC_MASK;
		conf->ht_capab |= HT_CAP_INFO_RX_STBC_12;
	}
	if (os_strstr(capab, "[RX-STBC123]")) {
		conf->ht_capab &= ~HT_CAP_INFO_RX_STBC_MASK;
		conf->ht_capab |= HT_CAP_INFO_RX_STBC_123;
	}
}

static int hostapd_config_vht_capab(struct hostapd_config *conf,
				    const char *capab)
{
	if (os_strstr(capab, "[RX-STBC-1]"))
		conf->vht_capab |= VHT_CAP_RXSTBC_1;
	if (os_strstr(capab, "[RX-STBC-12]"))
		conf->vht_capab |= VHT_CAP_RXSTBC_2;
	if (os_strstr(capab, "[RX-STBC-123]"))
		conf->vht_capab |= VHT_CAP_RXSTBC_3;
	if (os_strstr(capab, "[RX-STBC-1234]"))
}
```

Signed-off-by: Sean Khan <datapronix@protonmail.com>
Link: https://github.com/openwrt/openwrt/pull/18013
Signed-off-by: John Crispin <john@phrozen.org>