Fix compile issue with missing/needed <endian.h> includes

[skilau]

Without adding in the include of <endian.h> in 2 files that use functions/defines from it, we end up getting compiler errors and linking errors. (Specifically, the htobe16 and be64toh functions/defines, which exist in <endian.h>)

Including the compile log below, just to show the errors that we get:

[22/132] Building C object CMakeFiles/libwsbrd.dir/common/crypto/ieee80211.c.o
common/crypto/ieee80211.c: In function ‘ieee80211_is_mic_valid’:
common/crypto/ieee80211.c:39:31: warning: implicit declaration of function ‘htobe16’ [-Wimplicit-function-declaration]
   39 |         .packet_body_length = htobe16(sizeof(*frame) + data_len),
      |                               ^~~~~~~

[57/132] Building C object CMakeFiles/libwsbrd.dir/common/ieee802154_frame.c.o
common/ieee802154_frame.c: In function ‘ieee802154_frame_parse’:
common/ieee802154_frame.c:204:25: warning: implicit declaration of function ‘htobe64’ [-Wimplicit-function-declaration]
  204 |         hdr->dst.be64 = htobe64(iobuf_pop_le64(&iobuf));
      |                         ^~~~~~~

common/ieee802154_frame.c: In function ‘ieee802154_frame_write_hdr’:
common/ieee802154_frame.c:274:32: warning: implicit declaration of function ‘be64toh’ [-Wimplicit-function-declaration]
  274 |         iobuf_push_le64(iobuf, be64toh(hdr->dst.be64));
      |                                ^~~~~~~