[syscalls][log] Remove log.h inclusion in garnet

zx_log_* were removed in favor of zx_debuglog_*. Remove the wrapper
header too now.

ZX-2184 #comment [syscalls][log] Remove log.h inclusion in garnet

Test: CQ
Change-Id: I5859b0df252d1f2393ef28bd5d712e525039a827
2 files changed