lm4: workaround to force __enter_hibernate in SRAM
lm4: workaround to force __enter_hibernate in SRAM

The new toolchain is putting again the __enter_hibernate function in
flash (.text) rather than in SRAM (.iram.text) after inlining both the
hibernate() and __enter_hibernate() function.
Workaround this issue by forcing "noinline" on __enter_hibernate().

Signed-off-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

BRANCH=all
BUG=chrome-os-partner:35774
TEST=make BOARD=samus dis
and check the disassembly, the __enter_hibernate is called in SRAM
through a veneer.

Change-Id: I015928ebe18ba8fd93252eece3e8a0fcf4b2a037
Reviewed-on: https://chromium-review.googlesource.com/242691
Trybot-Ready: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>
Tested-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Commit-Queue: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

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