net/thunderx: add missing external dependency
net/thunderx: add missing external dependency

To prevent compile error when compiling for shared library:
nicvf_hw.o: In function `nicvf_qsize_regbit':
nicvf_hw.c:(.text+0xe64): undefined reference to `log2'
nicvf_hw.o: In function `nicvf_rss_reta_update':
nicvf_hw.c:(.text+0x19dd): undefined reference to `log2'
nicvf_hw.o: In function `nicvf_rss_reta_query':
nicvf_hw.c:(.text+0x1acb): undefined reference to `log2'

Fixes: e438796617dc ("net/thunderx: add PMD skeleton")

Signed-off-by: Ferruh Yigit <ba8734c3c506d2e3557bd4ac8fdaccd25bdb9aa7@intel.com>
Acked-by: Jerin Jacob <5bca7d2a432bc0f5422b70b2701a4e4fa32edd00@caviumnetworks.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk