ubi: Replace erase_block() with sync_erase()

mainline inclusion
from mainline-v6.7-rc1
commit c19286d70aaa361cdb073a68a1f66232c359e2fd
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I9195H
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c19286d70aaa361cdb073a68a1f66232c359e2fd



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Since erase_block() has same logic with sync_erase(), just replace it
with sync_erase(), also rename 'sync_erase()' to 'ubi_sync_erase()'.

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>