core/flash: Fix invalid try_lock check in flash_nvram_write
core/flash: Fix invalid try_lock check in flash_nvram_write

We have the logic inverted here.

Signed-off-by: Jeremy Kerr <68a658b44bbaefab3ef5cd231967195fc0ff9d69@ozlabs.org>

legoater/skiboot,legoater/skiboot,cyrilbur-ibm/skiboot,jk-ozlabs/skiboot,shenki/skiboot,shenki/skiboot,ddstreet/skiboot,legoater/skiboot,stewart-ibm/skiboot,cyrilbur-ibm/skiboot,mikey/skiboot,stewart-ibm/skiboot,csmart/skiboot,open-power/skiboot,shenki/skiboot,csmart/skiboot,open-power/skiboot,open-power/skiboot,jk-ozlabs/skiboot,qemu/skiboot,stewart-ibm/skiboot,jk-ozlabs/skiboot,csmart/skiboot,qemu/skiboot,qemu/skiboot,shenki/skiboot,mikey/skiboot,cyrilbur-ibm/skiboot,legoater/skiboot,qemu/skiboot,qemu/skiboot,ddstreet/skiboot,legoater/skiboot,open-power/skiboot,mikey/skiboot,apopple/skiboot,apopple/skiboot,apopple/skiboot,shenki/skiboot,ddstreet/skiboot,open-power/skiboot