scripts: gcc-wrapper: bypass forbidden warnings with gcc5

Bypass forbidden warnings in code coming from upstream in order to
avoid compilation errors with gcc5.
sysrq.c:956:33: warning: array subscript is above array bounds
hci_sock.c:980:8: warning: passing argument 2 of 'hci_test_bit'
discards 'const' qualifier from pointer target type

Change-Id: I5056078112fdc457c424c0f49c4dca70c6b97c29
Signed-off-by: Se Wang (Patrick) Oh <sewango@codeaurora.org>