wifi: iwlwifi: move pcie content to pcie internal transport

wifi: iwlwifi: move pcie content to pcie internal transport

The iwl_txq, iwl_pcie_first_tb_buf and iwl_pcie_txq_entry don't need to
be exported to the op_mode in iwl-trans.h. Declare those in the
transport's internal header file to avoid pollution.
iwl_trans_pcie_send_hcmd can also be moved to the internal header file.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Link: https://patch.msgid.link/20260517100550.208921548b4b.I76b1ac8499275e6d231880861e3843278f278c34@changeid
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>