msm: 8064: add configuration to prevent asserting ap2m_errfatal

For the DSDA2 target with two external modems, independent
subsystem restart of each modem is required. This flag is
used by the mdm driver to prevent it from asserting the
ap2mdm_errfatal during subsystem shutdown for the DSDA2 target,
otherwise both modems would reset because they share the same
gpio.

Change-Id: I27aedaa2b1b8756079710e41d8a4a9572b8ff83a
Signed-off-by: Joel King <joelking@codeaurora.org>