runtime: Fix alloc-dealloc-mismatch in host_buffer

ERROR: AddressSanitizer: alloc-dealloc-mismatch (operator new [] vs operator delete) on 0x631000028800
    #0 0x7f87c88129d7 in operator delete(void*, unsigned long) (/lib64/libasan.so.6+0xad9d7)
    gnuradio#1 0x7f87c5378c57 in std::default_delete<char>::operator()(char*) const /usr/include/c++/10/bits/unique_ptr.h:85
    gnuradio#2 0x7f87c5378c57 in std::unique_ptr<char, std::default_delete<char> >::~unique_ptr() /usr/include/c++/10/bits/unique_ptr.h:361
    gnuradio#3 0x7f87c5378c57 in gr::host_buffer::~host_buffer() /home/user/src/gnuradio/gnuradio-runtime/lib/host_buffer.cc:65
    gnuradio#4 0x7f87c5384654 in gr::host_buffer::~host_buffer() /home/user/src/gnuradio/gnuradio-runtime/lib/host_buffer.cc:65

0x631000028800 is located 0 bytes inside of 65536-byte region [0x631000028800,0x631000038800)
allocated by thread T0 here:
    #0 0x7f87c8811cb7 in operator new[](unsigned long) (/lib64/libasan.so.6+0xaccb7)
    gnuradio#1 0x7f87c5377a7a in gr::host_buffer::do_allocate_buffer(unsigned long, unsigned long) /home/user/src/gnuradio/gnuradio-runtime/lib/host_buffer.cc:123
    gnuradio#2 0x7f87c56deebf  (/home/user/src/gnuradio/build/gnuradio-runtime/lib/libgnuradio-runtime.so.3.10.0git+0x3475ebf)

Signed-off-by: Vasil Velichkov <vvvelichkov@gmail.com>

gnuradio-runtime/include/gnuradio/host_buffer.h

@@ -95,7 +95,7 @@ class GR_RUNTIME_API host_buffer : public buffer_single_mapped
 
 private:
     // This is the simulated device buffer
-    std::unique_ptr<char> d_device_buf;
+    std::unique_ptr<char[]> d_device_buf;
     char* d_device_base;
 
     /*!