wifi: ath11k: Fix scan request param frame size warning

Following warning was observed

drivers/net/wireless/ath/ath11k/mac.c:2351:1: warning: the frame
size of 1184 bytes is larger than 1024 bytes [-Wframe-larger-than=]

A local variable is declared with a size larger than 1024 bytes
this causing a compilation warning. Change the local variable to
heap memory to fix the warning.

Tested-on: IPQ8074 AHB WLAN.HK.2.7.0.1-01701-QCAHKSWPL_SILICONZ-1 v2

Signed-off-by: Karthikeyan Kathirvel <quic_kathirve@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20221205192125.13533-1-quic_kathirve@quicinc.com