runtime: add missing //go:nosplit for efaceOf

[honsunrise]

This fix prevents additional stack checking code from being
generated on func efaceOf to avoid unexpected growth of stack
in child process.

Fixes #48967

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[honsunrise]

@googlebot I signed it!

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[honsunrise]

@googlebot I fixed it.

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Patch Set 1:

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Patch Set 1:

(1 comment)

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Patch Set 1:

(1 comment)

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Patch Set 3:

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