mailbox: pcc: Fix spelling mistake "Plaform" -> "Platform"

mainline inclusion
from mainline-v6.1-rc1
commit 8ac11110
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6Z91B
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.3-rc2&id=8ac1111055afc863c78e389b051d843babbf2ca9



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There is a spelling mistake in a pr_err message. Fix it.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>