buddy: Check zalloc() return value
buddy: Check zalloc() return value

All callers of buddy_create() are correctly checking return value.

Found by static analysis

Fixes: 8594b9c5bd456205255ea2241ba224f47480efad
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

qemu/skiboot,qemu/skiboot,mikey/skiboot,open-power/skiboot,shenki/skiboot,legoater/skiboot,mikey/skiboot,open-power/skiboot,qemu/skiboot,qemu/skiboot,stewart-ibm/skiboot,stewart-ibm/skiboot,legoater/skiboot,open-power/skiboot,qemu/skiboot,mikey/skiboot,shenki/skiboot,legoater/skiboot,legoater/skiboot,stewart-ibm/skiboot,open-power/skiboot,shenki/skiboot,shenki/skiboot,open-power/skiboot,legoater/skiboot,shenki/skiboot