Typedef apb_req_t
typedef struct packed {
addr_t paddr; // same as AXI4-Lite
axi_pkg::prot_t pprot; // same as AXI4-Lite, specification is the same
logic psel; // onehot, one psel line per connected APB4 slave
logic penable; // enable signal shows second APB4 cycle
logic pwrite; // write enable
data_t pwdata; // write data, comes from W channel
strb_t pstrb; // write strb, comes from W channel
} apb_req_t;