mfd: ab3100-core.c: Fix multiple warnings reported by Checkpatch

WARNING: Missing a blank line after declarations
+       struct ab3100 *ab3100 = dev_get_drvdata(dev->parent);
+       if (!ab3100->startup_events_read)

WARNING: Possible unnecessary 'out of memory' message
+       if (!ab3100) {
+               dev_err(&client->dev, "could not allocate AB3100 device\n");

WARNING: else is not generally useful after a break or return
+                               break;
+                       } else {

total: 0 errors, 3 warnings, 996 lines checked

Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>