sound: rawmidi: Move spinlock under realloc_mutex

A merge conflict resolution of commit e57f781805f0 ("ANDROID: sound:
rawmidi: Hold lock around realloc") placed a realloc_mutex lock
inside of a runtime->lock irq spinlock. The mutex lock has to
encompass the spinlock to avoid attempts to sleep in an invalid
context.

Change-Id: I9333a01615c54fea3788f32955f40ae4b7a812a0
Signed-off-by: Dennis Cagle <dcagle@codeaurora.org>