hw/misc: cast rpm to uint64_t

hw/misc: cast rpm to uint64_t

The value of an arithmetic expression
'rpm * NPCM7XX_MFT_PULSE_PER_REVOLUTION' is a subject
to overflow because its operands are not cast to
a larger data type before performing arithmetic. Thus, need
to cast rpm to uint64_t.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Tigran Sogomonian <tsogomonian@astralinux.ru>
Reviewed-by: Patrick Leis <venture@google.com>
Reviewed-by: Hao Wu <wuhaotsh@google.com>
Message-id: 20241226130311.1349-1-tsogomonian@astralinux.ru
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>