Strip debug symbols from modules

The size of the ramdisk has greatly increased, which can be a source of
boot time regressions. Strip the modules of debug symbols for the vendor
ramdisk and vendor partitions; vendor stripping can be skipped via BOARD
config.

Bug: 156395749
Signed-off-by: J. Avila <elavila@google.com>
Change-Id: I7d1736da1599e265793173a741053d8a09f1622f