dspcrashd: fix dump_dmesg return type

Summary:
hardware/msm7k/dspcrashd/dspcrashd.c:74:5: error: void function 'dump_dmesg' should not return a value [-Wreturn-type]
    return 0;
    ^      ~

Test Plan: verified, not sure what legacy devices we have that still use msm7k hw.

Reviewers: randall.rushing, jriordan001

Differential Revision: http://review.codefirex.com/D294