* Mark unused parameters as unused

In Android, we are building libbpf with -Wunused-parameter, mark the
parameters in bpf_detach_tracepoint to prevent errors.

Change-Id: I2d0011746af80898e55d456b973a95330ce6be71
Signed-off-by: Joel Fernandes <joel@joelfernandes.org>

* Avoid void pointer arithmetic

In Android, we build libbpf with -Wpointer-arith, this causes warnings
as below. Avoid void pointer arithmetic to prevent the warning.

external/bcc/src/cc/perf_reader.c:189:26: error: arithmetic on a pointer
to void is a GNU extension [-Werror,-Wpointer-arith] memcpy(reader->buf
+ len, base, e->size - len);                               ~~~~~~~~~~~ ^

Change-Id: If06535459473c78799b38119786a91e74a208895
Signed-off-by: Joel Fernandes <joel@joelfernandes.org>

* Cast correctly for unsigned long format specifier

In Android, -Wformat gets passed to the compiler causing a warning. Fix
it by casting.

external/bcc/src/cc/libbpf.c:972:58: error: format specifies type
'unsigned long' but the argument has type 'uint64_t' (aka 'unsigned lo
ng long') [-Werror,-Wformat]

Change-Id: I5e70eeff983f20a0b921e81aee7ddbee6d7de2b3
Signed-off-by: Joel Fernandes <joel@joelfernandes.org>