wifi: cfg80211: pmsr: use correct nla_get_uX functions

The commit 9bb7e0f2 ("cfg80211: add peer measurement with FTM
initiator API") defines four attributes NL80211_PMSR_FTM_REQ_ATTR_
{NUM_BURSTS_EXP}/{BURST_PERIOD}/{BURST_DURATION}/{FTMS_PER_BURST} in
following ways.

static const struct nla_policy
nl80211_pmsr_ftm_req_attr_policy[NL80211_PMSR_FTM_REQ_ATTR_MAX + 1] = {
    ...
    [NL80211_PMSR_FTM_REQ_ATTR_NUM_BURSTS_EXP] =
        NLA_POLICY_MAX(NLA_U8, 15),
    [NL80211_PMSR_FTM_REQ_ATTR_BURST_PERIOD] = { .type = NLA_U16 },
    [NL80211_PMSR_FTM_REQ_ATTR_BURST_DURATION] =
        NLA_POLICY_MAX(NLA_U8, 15),
    [NL80211_PMSR_FTM_REQ_ATTR_FTMS_PER_BURST] =
        NLA_POLICY_MAX(NLA_U8, 31),
    ...
};

That is, those attributes are expected to be NLA_U8 and NLA_U16 types.
However, the consumers of these attributes in `pmsr_parse_ftm` blindly
all use `nla_get_u32`, which is incorrect and causes functionality issues
on little-endian platforms. Hence, fix them with the correct `nla_get_u8`
and `nla_get_u16` functions.

Fixes: 9bb7e0f2

 ("cfg80211: add peer measurement with FTM initiator API")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Link: https://msgid.link/20240521075059.47999-1-linma@zju.edu.cn
Signed-off-by: Johannes Berg <johannes.berg@intel.com>